Performance of adaptive bayesian equalizers in outdoor environments

Outdoor communications are affected by multipath propagation that imposes an upper limit on the system data rate and restricts possible applications. In order to overcome the degrading effect introduced by the channel, conventional equalizers implemented with digital filters have been traditionally used. A new approach based on neural networks is considered. In particular, the behavior of the adaptive Bayesian equalizer implemented by means of radial basis functions applied to the channel equalization of radio outdoor environments has been analyzed. The method used to train the equalizer coefficients is based on a channel response estimation. We compare the results obtained with three channel estimation methods: the least sum of square errors (LSSE) channel estimation algorithm, recursive least square (RLS) algorithm employed only to obtain one channel estimation and, finally, the RLS algorithm used to estimate the channel every decided symbol for the whole frame.Peer ReviewedPostprint (published version

Performance of blind equalization with higher order statistics in indoor radio environments

This paper analyzes the performance of blind equalization using the complex cepstrum of third-order moments applied to 4-QAM time division multiple access (TDMA) indoor radio communication systems. In particular, we have modeled a dispersive indoor channel with Rice statistics. We used the blind algorithms to estimate the channel-impulse response, and from this, we computed the equalizer coefficients using a classical minimum mean square error (MMSE) algorithm. In order to evaluate the system performance, we calculated the bit error rate (BER) of a decision feedback equalizer (DFE) that uses a tricepstrum algorithm to estimate the channel-impulse response. The results are compared with those obtained using a least sum of square errors (LSSE) algorithm as a channel estimator and considering the exact channel response. The results obtained show that this kind of blind equalizer performs better than the more classically trained equalizer when Rice channels with a strong direct path and signal-to-noise ratios (SNR’s) lower than 20 dB are taken into account. However, some problems relating to the length of time needed for convergence must be solved.Peer Reviewe

Alternativas en el desarrollo de aplicaciones para móviles

Cuando se alcanza la etapa de madurez del mercado GSM, como sería el caso de España, se impulsan nuevos servicios y aplicaciones para móviles, cuyo desarrollo puede fundamentarse en diversas tecnologías. En esta comunicación se presentan y evalúan tres alternativas mediante la implantación de servicios de información bursátil y ticketing, basadas en SIMToolkit, WAP o aplicaciones ad-hoc.Peer ReviewedPostprint (published version

On the feasibility of Bluetooth, Zigbee and IEEE 802.15.4 technologies on board high speed trains

This paper studies the feasibility of using low-power wireless technologies such as Bluetooth, IEEE 802.15.4 and ZigBee in high-speed railway scenarios that involve bidirectional land-to-train communication. The presented results have been obtained through experimental tests conducted at the high-speed railway line connecting Madrid to Barcelona. A multiplatform communication system has been installed in a high-speed train, circulating at velocities up to 300 km/h, whereas autonomous devices have been disseminated along of the railway path to communicate with the onboard devices. The conclusions drawn from this work will be used as guidelines for the future implementation of autonomous communication platforms for high-speed rail connectivity.Postprint (author’s final draft

Economic rationale shaping music teacher education: the case of Spain

This article discusses the literature on music teacher education programmes for mainstream education in order to undertake critical reflection on what we are doing and why in our university classrooms, what theories are implicit and what could be done to improve our programmes. After analysis, mainly from European contexts, and considering the Spanish one in particular, we find an influence of the economic – and, ultimately, political – rationale on substantial aspects, manifested in apparent disjunctions between musical and educational features, as well as in formal issues, fundamentally due to the European Higher Education Area. In the end, it is concluded that, without renouncing the economic aspects, curricula should be more addressed towards the integration of pedagogical and musical knowledge, and the treatment of aspects related to social justice, if we do not want an uncritical reproduction of rationalities that are often obsolete in the training of pre-service music teachers.Proyecto de investigación I+D EDU2017-84782-P sobre Formación del Profesorado y Música en la Sociedad y en la Economía del Conocimiento, financiado por el Ministerio de Economía y Competitividad del Gobierno de España.Universidad de Granad

Multipolling and OFDMA Reservation Protocol for IEEE 802.11 Networks

This paper presents an efficient multipolling scheme that improves the IEEE 802.11 MAC protocol efficiency and does not suffer from the hidden terminal problem or inefficient channel usage problems. To design an efficient polling scheme, the access point (AP) needs to obtain information about the current transmission status and channel state for each station. In this new scheme, we propose the use of multipolling frames in the downlink and Orthogonal Frequency Division Multiple Access (OFDMA) for the uplink reservation frames in order to reduce signaling overhead.Postprint (published version

A low-cost tracking system for running race applications based on bluetooth low energy technology

Timing points used in running races and other competition events are generally based on radio-frequency identification (RFID) technology. Athletes’ times are calculated via passive RFID tags and reader kits. Specifically, the reader infrastructure needed is complex and requires the deployment of a mat or ramps which hide the receiver antennae under them. Moreover, with the employed tags, it is not possible to transmit additional and dynamic information such as pulse or oximetry monitoring, alarms, etc. In this paper we present a system based on two low complex schemes allowed in Bluetooth Low Energy (BLE): the non-connectable undirected advertisement process and a modified version of scannable undirected advertisement process using the new capabilities present in Bluetooth 5. After fully describing the system architecture, which allows full real-time position monitoring of the runners using mobile phones on the organizer side and BLE sensors on the participants’ side, we derive the mobility patterns of runners and capacity requirements, which are determinant for evaluating the performance of the proposed system. They have been obtained from the analysis of the real data measured in the last Barcelona Marathon. By means of simulations, we demonstrate that, even under disadvantageous conditions (50% error ratio), both schemes perform reliably and are able to detect the 100% of the participants in all the cases. The cell coverage of the system needs to be adjusted when non-connectable process is considered. Nevertheless, through simulation and experimental, we show that the proposed scheme based on the new events available in Bluetooth 5 is clearly the best implementation alternative for all the cases, no matter the coverage area and the runner speed. The proposal widely exceeds the detection requirements of the real scenario, surpassing the measured peaks of 20 sensors per second incoming in the coverage area, moving at speeds that range from 1.5 m/s to 6.25 m/s. The designed real test-bed shows that the scheme is able to detect 72 sensors below 600 ms, fulfilling comfortably the requirements determined for the intended application. The main disadvantage of this system would be that the sensors are active, but we have proved that its consumption can be so low (9.5 µA) that, with a typical button cell, the sensor battery life would be over 10,000 h of use.Peer ReviewedPostprint (published version

Bluetooth Low Energy sensor networks for railway applications

©2017 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.This paper analyzes the viability of Bluetooth Low Energy (BLE) as the enabling technology in railway scenarios to allow sensor data transmission from ground to train. This proposal is based on using the broadcasting capabilities introduced by the Bluetooth specifications since v4.0. The last version, v5.0, extends the range the speed and the broadcast capacity. However, due to its recent publication it is hard to find real devices with it implemented in the market. The proposed schema has been validated by means of experimental measurements using v4.2.Peer ReviewedPostprint (author's final draft

Proposal and evaluation of BLE discovery process based on new features of bluetooth 5.0

The device discovery process is one of the most crucial aspects in real deployments of sensor networks. Recently, several works have analyzed the topic of Bluetooth Low Energy (BLE) device discovery through analytical or simulation models limited to version 4.x. Non-connectable and non-scannable undirected advertising has been shown to be a reliable alternative for discovering a high number of devices in a relatively short time period. However, new features of Bluetooth 5.0 allow us to define a variant on the device discovery process, based on BLE scannable undirected advertising events, which results in higher discovering capacities and also lower power consumption. In order to characterize this new device discovery process, we experimentally model the real device behavior of BLE scannable undirected advertising events. Non-detection packet probability, discovery probability, and discovery latency for a varying number of devices and parameters are compared by simulations and experimental measurements. We demonstrate that our proposal outperforms previous works, diminishing the discovery time and increasing the potential user device density. A mathematical model is also developed in order to easily obtain a measure of the potential capacity in high density scenarios.Peer ReviewedPostprint (published version

Design rules for antenna placement on MIMO systems

In recent works, it is demonstrated that, depending on the different spatial distributions and distance between elements, there exists a different true polarization diversity (TPD) configuration that provides a high improvement in terms of capacity. This means that it is necessary to choose the appropriate TPD configuration to maximize the multiple-input-multiple-output (MIMO) capacity. In this work, a genetic algorithm is used to optimize the element positions for four new different configurations in combination with the TPD technique. It is shown that, for some configurations, the same polarization option is always found to reach the maximum capacity. Based on this, some novel design rules are provided to maximize MIMO capacity when the area for placing the antennas is very small. This is the case for most of the wireless devices, where the antenna design and location is one of the latest design constraints to be taken into consideration in the device design