Open Access
Impact of body wearable sensor positions on UWB ranging
(IEEE, 2019) Otim, Timothy; Bahillo, Alfonso; Díez, Luis E.; López Iturri, Peio; Falcone Lanas, Francisco; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In recent years, Ultrawideband (UWB) has become a very popular technology for time of flight (TOF) based localization and tracking applications but its human body interactions have not been studied yet extensively. Most UWB systems already proposed for pedestrian ranging have only been individually evaluated for a particular wearable sensor position. It is observed that wearable sensors mounted on or close to the human body can raise line-of-sight (LOS), quasi-line-of-sight (QLOS), and non-line-of-sight (NLOS) scenarios leading to significant ranging errors depending on the relative heading angle (RHA) between the pedestrian, wearable sensor, and anchors. In this paper, it is presented that not only does the ranging error depend on the RHA, but on the position of the wearable sensors on the pedestrian. Seven wearable sensor locations namely, fore-head, hand, chest, wrist, arm, thigh and ankle are evaluated and a fair comparison is made through extensive measurements and experiments in a multipath environment. Using the direction in which the pedestrian is facing, the RHA between the pedestrian, wearable sensor, and anchors is computed. For each wearable sensor location, an UWB ranging error model with respect to the human body shadowing effect is proposed. A final conclusion is drawn that among the aforementioned wearable locations, the fore-head provides the best range estimate because it is able to set low mean range errors of about 20 cm in multipath conditions. The fore-head's performance is followed by the hand, wrist, ankle, arm, thigh, and chest in that order.
Open Access
FDTD and empirical exploration of human body and UWB radiation interaction on TOF ranging
(IEEE, 2019) Otim, Timothy; Bahillo, Alfonso; Díez, Luis E.; López Iturri, Peio; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In time-of-flight (TOF)-based human ranging systems, target sensors are often mounted on or close to the human body, which may raise non-line-of-sight (NLOS) cases and lead to significant ranging errors depending on the relative position between the body, transmitter (Tx), and receiver (Rx). In recent years, ultrawideband (UWB) has become a very popular technology for human TOF ranging, but its human body interactions have not been studied yet extensively. In this letter, the UWB and human body interaction is explored by the finite-difference time-domain (FDTD) technique, and the obtained E-field strength variation results are validated by means of commercially available UWB kits. Additionally, an UWB-ranging error model with respect to the human body shadowing effect is proposed and evaluated by extensive measurements, i.e., in indoor environments, line-of-sight (LOS) and NLOS are found to be well modeled by Gaussian and Gamma distributions, respectively, while in outdoor fields, LOS and NLOS are both modeled by Gaussian distributions. The main conclusion of this study is that there is a clear pattern between a gain in the E-field strength and TOF ranging errors. It can be established that in a worst-case scenario, a gain of 4–18 dB is observed, which corresponds to about 30–60 cm of TOF ranging errors.
Open Access
Ubiquitous connected train based on train-to-ground and intra-wagon communications capable of providing on trip customized digital services for passengers
(MDPI, 2014) Salaberria, Itziar; Perallos Ruiz, Asier; Azpilicueta Fernández de las Heras, Leyre; Falcone Lanas, Francisco; Carballedo, Roberto; Angulo Martínez, Ignacio; Elejoste Larrucea, Pilar; Bahillo, Alfonso; Astrain Escola, José Javier; Villadangos Alonso, Jesús; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Ingeniería Matemática e Informática; Matematika eta Informatika Ingeniaritza
During the last years, the application of different wireless technologies has been explored in order to enable Internet connectivity from vehicles. In addition, the widespread adoption of smartphones by citizens represents a great opportunity to integrate such nomadic devices inside vehicles in order to provide new and personalized on trip services for passengers. In this paper, a proposal of communication architecture to provide the ubiquitous connectivity needed to enhance the smart train concept is presented and preliminarily tested. It combines an intra-wagon communication system based on nomadic devices connected through a Bluetooth Piconet Network with a highly innovative train-to-ground communication system. In order to validate this communication solution, several tests and simulations have been performed and their results are described in this paper.
Open Access
Optimization and design of wireless systems for the implementation of context aware scenarios in railway passenger vehicles
(IEEE, 2017) Azpilicueta Fernández de las Heras, Leyre; Astrain Escola, José Javier; López Iturri, Peio; Granda, Fausto; Vargas Rosales, César; Villadangos Alonso, Jesús; Perallos Ruiz, Asier; Bahillo, Alfonso; Falcone Lanas, Francisco; Ingeniería Matemática e Informática; Matematika eta Informatika Ingeniaritza; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, intra-wagon wireless communication performance is analyzed, in order to account for inherent scenario complexity in the deployment phase of wireless systems toward the implementation of a context-aware environment. A real commercial passenger wagon has been simulated by means of an in-house-developed 3-D ray launching code, accounting for embedded wagon elements as well as variable user densities within the passenger wagon. Onboard measurements of a designed and deployed wireless sensor network are obtained, showing good agreement with wireless channel estimations for two different frequencies of operation. Energy consumption behavior and user density impact have also been analyzed and estimated as a function of network topology and the operational mode. These results can aid in wireless transceivers deployment configurations, in order to minimize power consumption, optimize interference levels, and increase overall service performance.
Open Access
Effects of the body wearable sensor position on the UWB localization accuracy
(MDPI, 2019) Otim, Timothy; Díez, Luis E.; Bahillo, Alfonso; López Iturri, Peio; Falcone Lanas, Francisco; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Over the years, several Ultrawideband (UWB) localization systems have been proposed and evaluated for accurate estimation of the position for pedestrians. However, most of them are evaluated for a particular wearable sensor position; hence, the accuracy obtained is subject to a given wearable sensor position. This paper is focused on studying the effects of body wearable sensor positions i.e., chest, arm, ankle, wrist, thigh, forehead, and hand, on the localization accuracy. According to our results, the forehead and the chest provide the best and worst body sensor location for tracking a pedestrian, respectively. With the wearable sensor at the forehead and chest position, errors lower than 0.35 m (90th percentile) and 4 m can be obtained, respectively. The reason for such a contrast in the performance lies in the fact that, in non-line-of-sight (NLOS) situations, the chest generates the highest multipath of any part of the human body. Thus, the large errors obtained arise due to the signal arriving at the target wearable sensor by multiple reflections from interacting objects in the environment rather than by direct line-of-sight (LOS) or creeping wave propagation mechanism.