Advanced HF Communications for Remote Sensors in Antarctica

The Antarctica is a continent mainly devoted to science with a big amount of sensors located in remote places for biological and geophysical purposes. The data from these sensors need to be sent either to the Antarctic stations or directly to the home country. For the last 15 years, La Salle has been working in the application of HF communications (3–30 MHz) with ionospheric reflection for data collection of remote sensors in Antarctica. We have developed and tested the several types of modulations, the frame structure, the radio-modem, and the antennas for two different scenarios. First, a long-range transequatorial (approximately 12,800 km) and low-power communication system is used as an alternative to satellites, which are often not visible from the poles. This distance is covered with a minimum of four hops with oblique incidence in the ionosphere. Second, a low-power system using near vertical incidence skywave (NVIS) communications provides coverage in a surface of approximately 200–250 km radius, a coverage much longer than any other systems operating in either the VHF or UHF band without the need of line of sight

Disseny de seqüències PN usant algoritmes genètics, ajust del control difús i optimització de l'estructura multiresolutiva per a la sincronització d'un receptor DS-SS en canal ionosfèric de llarga distància

L'estructura multiresolutiva proposada per Moran [1] té com a objectiu obtenir l'equilibri entre el cost computacional de l'adquisició sèrie i l'eficiència de l'adquisició paral•lela en sistemes d'espectre eixamplat de seqüència directa. L'adquisició i el posterior tracking són dos processos clau en la desmodulació del senyal d'espectre eixamplat, puix que sense una correcta sincronització aquesta és inviable. L'estructura multiresolutiva mostrà en la seva primera proposta un bon comportament en un canal ionosfèric de 800km [2], però el problema al que s'enfronta ara és més complex. Un canal ionosfèric des de l'Antàrtida a Catalunya, d'una longitud de 12700km, amb unes condicions de canal més agreujades per la distància i la variabilitat horària de la ionosfera en el trajecte de les ones. És amb aquest objectiu que aquest treball de tesi presenta millores a aquest algorisme d'adquisició i de seguiment amb els ulls posats en el problema a resoldre. S'han dissenyat seqüències PN adaptades a les necessitats de l'estructura multiresolutiva usant estratègies evolutives [3,4] i algorismes genètics [5], demanant a les seqüències pseudoaleatòries l'acompliment de més requisits que els originals de les seqüències PN. D'altra banda, també s'ha dissenyat un sistema d'estimació de la qualitat de l'adquisició i de control basat en lògica difusa [6], que permeti donar garanties de la robustesa de l'adquisició i alhora, millorar les prestacions de l'estructura reduint-ne el cost computacional. Finalment, s'ha realitzat un refinament del funcionament de l'estructura multiresolutiva, ajustant-ne els paràmetres d'aprenentatge dels filtres adaptatius de la mateixa per al canal ionosfèric i afegint-li la prestació de funcionar com a detector RAKE, que millora la qualitat de les dades desmodulades. Aquests nous dissenys i millores han estat contrastats amb l'estructura multiresolutiva original [1] i amb d'altres algorismes d'adquisició adaptatius basats en filtres LMS [7,8] i s'ha demostrat que les aportacions realitzades en aquest treball permeten obtenir un millor rendiment en les condicions de transmissió abordades. [1] J. A. Morán. Sistema ràpid d’adquisició per transmissió DS-SS sobre canal ionosfèric. Tesi Doctoral, Enginyeria i Arquitectura La Salle. Universitat Ramon Llull, Barcelona (Espanya), 2001. [2] J.A. Morán, J.C. Socoró, X. Jové, J.L. Pijoan i F. Tarrés. Multiresolution Adaptive Structure for acquisition in DS-SS receivers. International Conference on Acoustics, Speech and Signal Processing (ICASSP). Salt Lake City (EUA), 2001. [3] I. Rechenberg. Evolutionsstrategie: Optimierung technischer Systeme nach Prinzipiender biologischen Evolution. Frommann-Holzboog, Alemanya, 1973. [4] H.P. Schwefel. Evoluitonsstrategie und numerische Optimierung. Tesi Doctoral, Technische Universitat Berlin, Berlin (Alemanya), 1975. [5] D. E. Goldberg. Genetic Algorithms in Search, Optimization and Machine Learning. Addison-Wesley, 1989. [6] L.A. Zadeh. Fuzzy Sets. IEEE Trans. on Information and Control, 8:338–353, 1965. [7] M.G. El-Tarhuni. Application of Adaptive Filtering to Direct-Sequence Spread-Spectrum Code Synchronization. Tesi Doctoral, Carleton University, 1997. [8] M. Han, T. Yu, C. Kang i D. Hong. A New Adaptive Code-Acquisition Algorithm Using Parallel Subfilter Structure. IEEE Transactions on Vehicular Technology, 55(6):1790–1796, Novembre 2006.La estructura multiresolutiva propuesta por Moran [1] tiene como objetivo obtener el equilibrio entre el coste computacional de la adquisición serie y la eficiencia de la adquisición paralela en sistemas de espectro ensanchado de secuencia directa. La adquisición y el posterior tracking son dos procesos clave en la demodulación de la señal de espectro ensanchado, puesto que sin una correcta sincronización ésta es inviable. La estructura multiresolutiva mostró en su primera propuesta un buen comportamiento en un canal ionosférico de 800km [2], pero el problema al que se enfronta ahora es más complejo. Un canal ionosférico desde la Antártida a Catalunya, con una longitud de 12700km, con unas condiciones de canal más agravadas por la distancia y la variabilidad horaria de la ionosfera en el trayecto de las ondas. Con este objetivo, este trabajo de tesis presenta mejoras a este algoritmo de adquisición y de seguimiento con la mirada puesta en el problema a resolver. Se han diseñado secuencias PN adaptadas a las necesidades de la estructura multiresolutiva usando estrategias evolutivas [3,4] y algoritmos genéticos [5], pidiendo a las secuencias pseudoaleatorias más requisitos que los habituales en las secuencias PN. Por otro lado, también se ha diseñado un sistema de estimación de la calidad en la adquisición y de control basado en lógica difusa [6], que permita dar garantías de la robustez en la adquisición y a su vez, mejorar las prestaciones de la estructura reduciendo el coste computacional. Finalmente, se ha realizado un ajuste del funcionamiento de la estructura multiresolutiva, ajustándose los parámetros de aprendizaje de los filtros adaptativos para el canal ionosférico y añadiendo la prestación de funcionar como detector RAKE, que mejora la calidad de los datos demodulados. Estos nuevos diseños y mejoras se han contrastado con la estructura multiresolutiva original [1] y con otros algoritmos de adquisición adaptativos basados en filtros LMS [7,8] y se ha demostrado que las aportaciones realizadas en este trabajo permiten obtener un mejor rendimiento en las condiciones de transmisión abordadas. [1] J. A. Morán. Sistema ràpid d’adquisició per transmissió DS-SS sobre canal ionosfèric. Tesis Doctoral, Enginyeria i Arquitectura La Salle. Universitat Ramon Llull, Barcelona (España), 2001. [2] J.A. Morán, J.C. Socoró, X. Jové, J.L. Pijoan i F. Tarrés. Multiresolution Adaptive Structure for acquisition in DS-SS receivers. International Conference on Acoustics, Speech and Signal Processing (ICASSP). Salt Lake City (EUA), 2001. [3] I. Rechenberg. Evolutionsstrategie: Optimierung technischer Systeme nach Prinzipiender biologischen Evolution. Frommann-Holzboog, Alemanya, 1973. [4] H.P. Schwefel. Evoluitonsstrategie und numerische Optimierung. Tesis Doctoral, Technische Universitat Berlin, Berlin (Alemanya), 1975. [5] D. E. Goldberg. Genetic Algorithms in Search, Optimization and Machine Learning. Addison-Wesley, 1989. [6] L.A. Zadeh. Fuzzy Sets. IEEE Trans. on Information and Control, 8:338–353, 1965. [7] M.G. El-Tarhuni. Application of Adaptive Filtering to Direct-Sequence Spread-Spectrum Code Synchronization. Tesis Doctoral, Carleton University, 1997. [8] M. Han, T. Yu, C. Kang i D. Hong. A New Adaptive Code-Acquisition Algorithm Using Parallel Subfilter Structure. IEEE Transactions on Vehicular Technology, 55(6):1790–1796, Noviembre 2006.The multiresolutive structure proposed by Moran [1] attempts to reach a compromise between the computational cost of serial acquisition schemes and acquisition efficiency of parallel systems in direct-sequence spread spectrum acquisition. Acquisition and subsequent tracking are two key processes in the signal demodulation, since without proper synchronization demodulation is impossible. The multiresolutive structure in Moran’s first proposal showed a good performance on an ionospheric channel of 800km [2], but the problem we face now is more complex. A ionospheric radio channel from the Antarctica to Catalonia, 12700km in length, with worsen channel conditions due to distance and time variability of the ionosphere along the paths of the radio waves. This thesis presents improvements to this algorithm acquisition and tracking system in the aim of facing those hard channel conditions. PN sequences are designed to satisfy the needs of the multiresolutive structure [ABM05, AFSB07] using evolutionary strategies [3, 4] and genetic algorithms [5], through adding more requirements than is usually demanded. On the other hand, a fuzzy logic [6] control block has been implemented to estimate the quality of acquisition and control, evaluate the robustness of the acquisition and improve the performance of the structure by reducing its computational load. Finally, the multiresolutive structure has been adjusted, setting new values for the adaptive filter convergence parameters that refer to the ionospheric radio channel and improving the demodulated data using a RAKE detector. The new multiresolutive structure has been compared to the original multiresolutive structure [1] and to other LMS-based adaptive acquisition algorithms [7,8]. The results show that the new multiresolutive structure is competitive when comparing the original structure and also in relation to other adaptive acquisition algorithms found in state-of-the-art. [1] J. A. Morán. Sistema ràpid d’adquisició per transmissió DS-SS sobre canal ionosfèric. PhD Thesis, Enginyeria i Arquitectura La Salle. Universitat Ramon Llull, Barcelona (Espanya), 2001. [2] J.A. Morán, J.C. Socoró, X. Jové, J.L. Pijoan i F. Tarrés. Multiresolution Adaptive Structure for acquisition in DS-SS receivers. International Conference on Acoustics, Speech and Signal Processing (ICASSP). Salt Lake City (EUA), 2001. [3] I. Rechenberg. Evolutionsstrategie: Optimierung technischer Systeme nach Prinzipiender biologischen Evolution. Frommann-Holzboog, Alemanya, 1973. [4] H.P. Schwefel. Evoluitonsstrategie und numerische Optimierung. Tesi Doctoral, Technische Universitat Berlin, Berlin (Alemanya), 1975. [5] D. E. Goldberg. Genetic Algorithms in Search, Optimization and Machine Learning. Addison-Wesley, 1989. [6] L.A. Zadeh. Fuzzy Sets. IEEE Trans. on Information and Control, 8:338–353, 1965. [7] M.G. El-Tarhuni. Application of Adaptive Filtering to Direct-Sequence Spread-Spectrum Code Synchronization. PhD Thesis, Carleton University, 1997. [8] M. Han, T. Yu, C. Kang i D. Hong. A New Adaptive Code-Acquisition Algorithm Using Parallel Subfilter Structure. IEEE Transactions on Vehicular Technology, 55(6):1790–1796, November 2006

Design of a Low-Cost Configurable Acoustic Sensor for the Rapid Development of Sound Recognition Applications

Concerned about the noise pollution in urban environments, the European Commission (EC) has created an Environmental Noise Directive 2002/49/EC (END) requiring Member states to publish noise maps and noise management plans every five years for cities with a high density of inhabitants, major roads, railways and airports. The END also requires the noise pressure levels for these sources to be presented independently. Currently, data measurements and the representations of the noise pressure levels in such maps are performed semi-manually by experts. This process is time and cost consuming, as well as limited to presenting only a static picture of the noise levels. To overcome these issues, we propose the deployment of Wireless Acoustic Sensor Networks with several nodes in urban environments that can enable the generation of real-time noise level maps, as well as detect the source of the sound thanks to machine learning algorithms. In this paper, we briefly review the state of the art of the hardware used in wireless acoustic applications and propose a low-cost sensor based on an ARM cortex-A microprocessor. This node is able to process machine learning algorithms for sound source detection in-situ, allowing the deployment of highly scalable sound identification systems

An Approach to Frequency Selectivity in an Urban Environment by Means of Multi-Path Acoustic Channel Analysis

The improvement of quality of life in the framework of the smart city paradigm cannot be limited to a set of objective measures carried out over several critical parameters (e.g., noise or air pollution). Noise disturbances depend not only on the equivalent level LAeq measured, but also on the spectral distribution of the sounds perceived by people. Propagation modelling to conduct auralization can be done either with geometrical acoustics or with wave-based methods, given the fact that urban environments are acoustically complex scenarios. In this work, we present a first analysis of the acoustic spectral distribution of street noise, based on the frequency selectivity of the urban outdoor channel and its corresponding coherence bandwidth. The analysis was conducted in the framework of the data collected in the Milan pilotWASN of the DYNAMAP LIFE project, with the use of three simulated acoustic impulse responses. The results show the clear influence of the evaluated coherence bandwidth of each of the simulated channels over real-life acoustic samples, which leads us to the conclusion that all raw acoustic samples have to be considered as wide-band. The results also depict a dependence of accumulated energy at the receiver with the coherence bandwidth of the channel. We conclude that, the higher the delay spread of the channel, the narrower the coherence bandwidth and the higher the distortion suffered by acoustic signals. Moreover, the accumulated energy of the received signal along the frequency axis tends to differ from the accumulated energy of the transmitted signal when facing narrow coherence bandwidth channels; whereas the accumulated energy along the time axis diverges from the accumulated transmitted energy when facing wide coherence bandwidth channels

A Comparative Survey of Feature Extraction and Machine Learning Methods in Diverse Acoustic Environments

Acoustic event detection and analysis has been widely developed in the last few years for its valuable application in monitoring elderly or dependant people, for surveillance issues, for multimedia retrieval, or even for biodiversity metrics in natural environments. For this purpose, sound source identification is a key issue to give a smart technological answer to all the aforementioned applications. Diverse types of sounds and variate environments, together with a number of challenges in terms of application, widen the choice of artificial intelligence algorithm proposal. This paper presents a comparative study on combining several feature extraction algorithms (Mel Frequency Cepstrum Coefficients (MFCC), Gammatone Cepstrum Coefficients (GTCC), and Narrow Band (NB)) with a group of machine learning algorithms (k-Nearest Neighbor (kNN), Neural Networks (NN), and Gaussian Mixture Model (GMM)), tested over five different acoustic environments. This work has the goal of detailing a best practice method and evaluate the reliability of this general-purpose algorithm for all the classes. Preliminary results show that most of the combinations of feature extraction and machine learning present acceptable results in most of the described corpora. Nevertheless, there is a combination that outperforms the others: the use of GTCC together with kNN, and its results are further analyzed for all the corpora

An FPGA Platform Proposal for Real-Time Acoustic Event Detection: Optimum Platform Implementation for Audio Recognition with Time Restrictions

Nowadays, monitoring of people and events is a common matter in the street, in the industry or at home, and acoustic event detection is commonly used. This increases the knowledge of what is happening in the soundscape, and this information encourages any monitoring system to take decisions depending on the measured events. Our research in this field includes, on one hand, smart city applications, which aim is to develop a low cost sensor network for real time noise mapping in the cities, and on the other hand, ambient assisted living applications through audio event recognition at home. This requires acoustic signal processing for event recognition, which is a challenging problem applying feature extraction techniques and machine learning methods. Furthermore, when the techniques come closer to implementation, a complete study of the most suitable platform is needed, taking into account computational complexity of the algorithms and commercial platforms price. In this work, the comparative study of several platforms serving to implement this sensing application is detailed. An FPGA platform is chosen as the optimum proposal considering the application requirements and taking into account time restrictions of the signal processing algorithms. Furthermore, we describe the first approach to the real-time implementation of the feature extraction algorithm on the chosen platform

Smart Wireless Acoustic Sensor Network Design for Noise Monitoring in Smart Cities

This Special Issue is focused on all the technologies necessary for the development of anefficient wireless acoustic sensor network, from the first stages of its design to the tests conductedduring deployment; its final performance; and possible subsequent implications for authorities interms of the definition of policies. This Special Issue collects the contributions of several LIFE andH2020 projects aimed at the design and implementation of intelligent acoustic sensor networks, with afocus on the publication of good practices for the design and deployment of intelligent networks inany locations

Towards Automatic Bird Detection: An Annotated and Segmented Acoustic Dataset of Seven Picidae Species

Analysing behavioural patterns of bird species in a certain region enables researchers to recognize forthcoming changes in environment, ecology, and population. Ornithologists spend many hours observing and recording birds in their natural habitat to compare different audio samples and extract valuable insights. This manual process is typically undertaken by highly-experienced birders that identify every species and its associated type of sound. In recent years, some public repositories hosting labelled acoustic samples from different bird species have emerged, which has resulted in appealing datasets that computer scientists can use to test the accuracy of their machine learning algorithms and assist ornithologists in the time-consuming process of analyzing audio data. Current limitations in the performance of these algorithms come from the fact that the acoustic samples of these datasets combine fragments with only environmental noise and fragments with the bird sound (i.e., the computer confuses environmental sound with the bird sound). Therefore, the purpose of this paper is to release a dataset lasting more than 4984 s that contains differentiated samples of (1) bird sounds and (2) environmental sounds. This data descriptor releases the processed audio samples—originally obtained from the Xeno-Canto repository—from the known seven families of the Picidae species inhabiting the Iberian Peninsula that are good indicators of the habitat quality and have significant value from the environment conservation point of view

Ionospheric Narrowband and Wideband HF Soundings for Communications Purposes: A Review

High Frequency (HF) communications through ionospheric reflection is a widely usedtechnique specifically for maritime, aeronautical, and emergency services communication withremote areas due to economic and management reasons, and also as backup system. Although longdistance radio links can be established beyond line-of-sight, the availability, the usable frequenciesand the capacity of the channel depends on the state of the ionosphere. The main factors thataffect the ionosphere are day-night, season, sunspot number, polar aurora and earth magneticfield. These effects impair the transmitted wave, which suffers attenuation, time and frequencydispersion. In order to increase the knowledge of this channel, the ionosphere has been soundedby means of narrowband and wideband waveforms by the research community all over the worldin several research initiatives. This work intends to be a review of remarkable projects for verticalsounding with a world wide network and for oblique sounding for high latitude, mid latitude,and trans-equatorial latitud

An FPGA Scalable Software Defined Radio Platform Design for Educational and Research Purposes

In a digital modem design, the integration of the Analog to Digital Converters (ADC) and Digital to Analog Converters (DAC) with the core processor is usually a major issue for the designer. In this paper an FPGA scalable Software Defined Radio platform based on a Spartan-6 as a control unit is presented, developed for both educational and research purposes, which can fit the different application requirements in terms of analog front-end performance, processing unit and cost. The resolution and sampling frequency of the analog front-end are its main adjustable parameters. The processing core requirements involve the FPGA and the communication ports. A multidisciplinary working group was required to design a high performance system for both analog front-end and digital processing core in terms of signal integrity and electromagnetic compatibility. The platform has 5 different peripheral ports ranging from 16 kbps to 2.5 Gbps. The communication ports allow our students to develop a high range of applications for both on-site and online courses applying teaching methodology based on learning by doing using a real system to help them to reach other transversal skill