Héctor J. Pérez-Iglesias

Real-time personal protective equipment monitoring system

The use of personal protective equipment (PPEs) in the construction industry is necessary to guarantee the safety of the workers. However, this equipment is not usually worn properly. Nowadays, the only control performed over the use of PPEs consists of a visual inspection. This paper introduces a novel cyber-physical system (CPS) to check in real time how the PPEs are worn by the workers. In order to perform such a control, an architecture composed of a wireless local area network and a body area network is considered. A system prototype was developed by using Zigbee and RFID technologies that support the deployment of both kinds of networks. The worker carries a microcontroller-based device that detects the presence of the PPEs and sends a report to a central unit where alerts and historical data are generated. This paper is basically aimed at introducing the monitoring system, describing its hardware and software components, and analyzing the coverage and consumption of the workers device.

Blind channel identification in Alamouti coded systems: a comparative study of eigendecomposition methods in indoor transmissions at 2.4 GHz†

This paper focuses on blind channel estimation in Alamouti coded systems with one receiving antenna working in indoor scenarios where the flat fading assumption is reasonable. A comparative study of several channel estimation techniques in both simulated and realistic scenarios is presented. The tested methods exploit the orthogonality property of the Alamouti coded channel matrix, and are based on the eigendecomposition of a square matrix made up of second-order statistics (SOS) or higher order statistics (HOS) of the observed signals. An experimental evaluation is carried out on a testbed developed at the University of A Coruna (UDC) and operating at 2.4 GHz. The results show the superior performance of the SOS-based blind channel estimation technique in both line of sight (LOS) and non-LOS (NLOS) channels.

A distributed multilayer architecture enabling end-user access to MIMO testbeds

We propose a distributed multilayer architecture that provides user access to a MIMO testbed at the convenient abstraction level for researchers. This novel architecture releases the user from the need of low-level programming, making the MIMO testbed accessible through high level software (i.e. Matlab or similar). The layers of this architecture are highly decoupled among them, allowing us to run each layer on a different PC. Also, each layer permits independent extension or customisation as needed, for example to implement new testbed features such as a feedback channel or to deploy multiuser MIMO scenarios.

A Novel Video Coding Scheme based on Principal Component Analysis

This paper presents a novel video coding technique where most frames are represented as their projection onto a proper basis (eigenspace) computed using principal component analysis (PCA). Since a video sequence contains regions with high time variations, a learning procedure is used to obtain an adequate basis. We also introduce the idea of bidirectional predicted frames to denote those frames that can be estimated from the nearest past and future PCA coefficients. Experimental results show the high quality/compression achieved using the new scheme with different eigenspace updating algorithms

A Flexible Testbed for the Rapid Prototyping of MIMO Baseband Modules

Hardware platforms and testbeds are an essential tool to evaluate, in realistic scenarios, the performance of multiple-input-multiple-ouput (MIMO) systems. In this work we present a simple and easily reconfigurable 2 times 2 MIMO testbed for the rapid prototyping of the signal processing baseband functions. The signal generation module consists of a host PC equipped with a board that contains two high performance 100 MHz DACs and a 1 GB memory module that allows the transmission of extremely large frames of data. At the receiver side, we use another host PC equipped with two 105 MHz ADCs, another 1 GB memory module and a trigger that starts the acquisition process when the presence of signal is detected. The platform has been designed to operate at the ISM band of 2.4 GHz with a RF bandwidth of 20 MHz. In order to minimize the number of DAC and ADC circuits, signals are generated and acquired at an IF of 15 MHz. Upconversion to RF is performed with two RF vectorial signal generators (Agilent E4438C) and downconversion with two specific circuits designed from commercial components. Transmitter and receiver signal processing functions are implemented off-line in Matlab. To illustrate the performance and capabilities of the platform, we present the results of two experiments of a 2 times 2 MIMO transmission with Alamouti coding.

Performance of STBC transmissions with real data

This paper presents a comparative study of three Space-Time Block Coding (STBC) techniques in realistic indoor scenarios. In particular, we focus on the Alamouti orthogonal scheme considering two types of Channel State Information (CSI) estimation: a conventional pilot-aided technique and a new blind method based on Second Order Statistics (SOS). We also considered a Differential (non-coherent) Space-Time Block code (DSTBC) that can be optimally decoded without CSI estimation, although it incurs in a 3 dB loss in performance. Experimental evaluation is carried out with a flexible and easy-to-use 2 x 2 MIMO platform at 2.4 GHz. Results show the excellent performance of the blind channel estimation technique in either Line-Of-Sight (LOS) and Non-LOS (NLOS) indoor scenarios.

A blind channel estimation strategy for the 2X1 Alamouti system based on diagonalising 4th-order cumulant matrices

This paper presents a novel blind strategy to estimate the channel parameters in systems that make use of the well known Alamouti orthogonal space-time code to achieve full diversity. The channel parameters are obtained by computing the eigenvectors of a matrix containing 4th-order cumulants of the observations. The matrix to diagonalise is selected for each channel realization using a simple criterion based on the spread of its eigenvalues. Simulation results show that the performance of the proposed method is similar to the obtained using the well-known joint approximate diagonalisation of eigenmatrices (JADE) algorithm, with a low computational cost.

A comparative study of blind channel identification methods for Alamouti coded systems over indoor transmissions at 2.4 GHz

This paper focuses on blind channel estimation in Alamouti coded systems with one receiving antenna. We present a comparative study of several blind channel estimation techniques, based on high order statistics (HOS) and second order statistics (SOS), in realistic indoor scenarios. These methods are based on eigendecomposition of a square matrix formed with statistics of the observed signals. They also exploit the orthogonality property of the Alamouti coded channel matrix. Experimental evaluation is carried out using a MIMO testbed at the 2.4 GHz band. The results show the excellent performance of the SOS-based blind channel estimation technique in either line of sight (LOS) and Non-LOS (NLOS) indoor scenarios.

The ITG Smart Water Station

This work presents a smart water sensor station developed by Fundación Instituto Tecnológico de Galicia (ITG), Spain, for the monitoring of the water quality in remote places. The station is comprised by a hardware unit and a web platform, and it supports the following functionalities: sample measurement, local storage, power source, remote control, platform storage, and graphical representation in a web platform. A RESTful API based on Sensor Web Enablement (SWE) is employed to set the communication between the station and the web platform. The main advantage of the developed station is its versatility since different sensor technologies from different manufacturers can be embedded in the station.

A novel strategy for improving the quality of embedded zerotree wavelet images transmitted over alamouti coding systems

This work deals with the transmission of images, previously coded using the Embedded Zerotree Wavelet (EZW) transform, over wireless systems in which Space-Time Coding (STC) is used. It is shown how the system performance, measured in terms of Peak Signal to Noise Ratio (PSNR), can be improved using bit allocation strategies that take into account the special structure of the EZW bitstream, where the bits firstly allocated are associated to the lowest frequency subbands, and therefore, an error-free transmission of such bits will be crucial to appropriately recover the transmitted image.