Correlator implementation for orthogonal CSS used in an ultrasonic LPS

This paper presents a new architecture for the correlation of orthogonal complementary sets of sequences (OCSS) and their performance in an ultrasonic local positioning system (U-LPS). OCSS are sets of sequences whose addition of correlation functions has ideal properties, that makes interference-free code-division multiple access (CDMA) possible. They can be used to encode the signals emitted by a CDMA based U-LPS, enhancing the performance of such systems in terms of immunity against noise, multipath propagation, and near-far effect. Also, the orthogonality of the codes offers an operation resistance to multiaccess interference, which endows the U-LPS with the capability of simultaneous emission from different beacons. On the other hand, the detection of OCSS codes can be performed by means of efficient algorithms. This paper presents an optimization of previous proposals allowing the simultaneous correlation of OCSS by using fewer operations and memory elements. Furthermore, the hardware implementation of the proposed optimization is also addressed, and an U-LPS based on this proposal is presented.Fil: Peréz Rubio, M. Carmen. Universidad de Alcalá; EspañaFil: Sanz Serrano, Rebeca. Universidad de Alcalá; EspañaFil: Ureña Ureña, Jesús. Universidad de Alcalá; EspañaFil: Hernández Alonso, Álvaro. Universidad de Alcalá; EspañaFil: de Marziani, Carlos Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Álvarez Franco, Fernando J.. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ingeniería - Sede Comodoro; Argentin

Modeling the Behavior of an Underwater Acoustic Relative Positioning System Based on Complementary Set of Sequences

The great variability usually found in underwater media makes modeling a challenging task, but helpful for better understanding or predicting the performance of future deployed systems. In this work, an underwater acoustic propagation model is presented. This model obtains the multipath structure by means of the ray tracing technique. Using this model, the behavior of a relative positioning system is presented. One of the main advantages of relative positioning systems is that only the distances between all the buoys are needed to obtain their positions. In order to obtain the distances, the propagation times of acoustic signals coded by Complementary Set of Sequences (CSS) are used. In this case, the arrival instants are obtained by means of correlation processes. The distances are then used to obtain the position of the buoys by means of the Multidimensional Scaling Technique (MDS). As an early example of an application using this relative positioning system, a tracking of the position of the buoys at different times is performed. With this tracking, the surface current of a particular region could be studied. The performance of the system is evaluated in terms of the distance from the real position to the estimated one

Monitoring System for Elderly Care with Smartwatch and Smartphone

In recent years, mobile devices, such as Smartphones and Smartwatches, have increasingly been used as personal healthcare gadgets. This work presents the development of a monitoring system based on a software application over Android OS for mobile devices. The main goal is to use it as tool for monitoring and tracking elderly people. The proposed application allows to: detect falls to the ground of the users; monitor the heart rate; count the number of steps that the users perform during the day and also track their position on a map. Despite the presence of several cases of possible false positives (e.g. answer a call or sending a message could trigger a wrong detection of fall or increase the steps counters.), the results obtained show that it is possible, by using current mobile devices in the market, to supervise and track the user’s activities.IX Workshop Innovación en Sistemas de Software (WISS).Red de Universidades con Carreras en Informática (RedUNCI

Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation

In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others

Doppler resilience evaluation of different encoding techniques for underwater acoustic ranging systems

Underwater acoustic communication or localization systems can be affected by the Doppler effect when the receiver or emitter is in motion. In those cases, the use of an a appropiate encoding/modulating scheme play a pivotal role in the time of arrival estimations, avoiding the need of complex auxiliary Doppler compensation algorithms. This paper presents a Doppler resilience evaluation of Zadoff-Chu based schemes, modulated by phase modulation (QPSK), Orthogonal Frequency Division Multiplexing (OFDM) and Frequency Hopping Spread Spectrum (FHSS) modulation schemes. They are also compared to traditional binary Kasami codes modulated by BPSK. An underwater acoustic propagation model has been used to assessed the aforementioned schemes, to which the Doppler effect modeling has been also incorporated

Relative Positioning System Using Acoustic Sensors for Ubiquitous Computing Applications

Abstract. Systems that characterize the state of an entity or object are very important in the “smart spaces ” and “ubiquitous computing”; this information is usually known as the entity’s "context". Those applications, which describe or characterize these entities and interact with it, are often referred as "contextaware computing". One of the most important information is the position of an object with the purpose of offering the most suitable services to him. The mechanisms and techniques that determine these space relations are named “location"; and the computing applications, based on the position, are called “location-aware computing”. This article presents an indoor localization system in order to make a relative positioning among entities, fixed or mobile, without use an external infrastructure and only using acoustic transducers for their use in ubiquitous computing applications. Also, an analysis of the positioning algorithm, based on multidimensional scaling technique (MDS), is carried out in order to verify the errors in the position estimation when there are errors in the mechanism of ranging distances.

Design of modulation schemes in a Zadoff-Chu encoded ultrasonic positioning system

Comunicación presentada a las XXXIX Jornadas de Automática, celebradas en Badajoz del 5 al 7 de Septiembre de 2018 y organizada por la Universidad de Extremadura.Muchos sistemas de posicionamiento local ultrasónicos (U-LPS), consisten en varios transductores o balizas fijas emitiendo simultáneamente señales acústicas ultrasónicas, cuyo tiempo de llegada o diferencia de tiempos de llegada es estimado en un receptor móvil. El empleo de técnicas de codificación permite que el receptor sea capaz de separar cada una de ellas, identificar los transmisores y mitigar los efectos adversos que afecten a la señal, tales como el multicamino, el efecto cerca-lejos, la interferencia de acceso múltiple o el desplazamiento Doppler. El diseño de la forma de onda (codificación y modulación) desempeña un papel fundamental en la determinación del rendimiento de dicho sistema. En este trabajo se compara el rendimiento de tres técnicas de modulación (QPSK, OFDM y FHSS) para la transmisión de secuencias Zadoff-Chu (ZC) en un U-LPS. Las simulaciones realizadas indican que, en detección no coherente, la modulación QPSK de secuencias ZC ofrece mayor precisión en condiciones realistas que los otros esquemas de modulación.Many Ultrasonic Local Positioning Systems (U-LPS), consists of multiple fixed beacons that simultaneously emit ultrasonic signals whose times of arrival (ToA) are estimated at a mobile receiver. The ultrasonic signals can be encoded to allow separation of the signals at the receiver, identification of the transmitters, and mitigation of signal impairments such as multipath, the near-far effect, multiple access interference, and Doppler shift. Therefore, waveform design (coding and modulation) constitutes a key factor in determining the performance of such a system. This paper compares by simulation the performance of three modulation techniques (specifically QPSK, OFDM and FHSS) transmitting Zadoff-Chu (ZC) sequences in an U-LPS. Simulation results indicate that ZC coded QPSK modulation with non-coherent detection, offers greater accuracy under realistic conditions than the other modulation schemes.Ministerio Español de Economía y Competitividad. Proyecto SOC-PLC, ref. TEC2015- 64835-C3-2-R Universidad de Alcalá (CCGP2017-EXP/050) Universidad Nacional de la Patagonia San Juan Bosco de Argentina.peerReviewe

Design of modulation schemes in a Zadoff-Chu encoded ultrasonic positioning system

[Resumen] Muchos sistemas de posicionamiento local ultrasónicos (U-LPS), consisten en varios transductores o balizas fijas emitiendo simultáneamente señales acústicas ultrasónicas, cuyo tiempo de llegada o diferencia de tiempos de llegada es estimado en un receptor móvil. El empleo de técnicas de codificación permite que el receptor sea capaz de separar cada una de ellas, identificar los transmisores y mitigar los efectos adversos que afecten a la señal, tales como el multicamino, el efecto cerca-lejos, la interferencia de acceso múltiple o el desplazamiento Doppler. El diseño de la forma de onda (codificación y modulación) desempeña un papel fundamental en la determinación del rendimiento de dicho sistema. En este trabajo se compara el rendimiento de tres técnicas de modulación (QPSK, OFDM y FHSS) para la transmisión de secuencias Zadoff-Chu (ZC) en un U-LPS. Las simulaciones realizadas indican que, en detección no coherente, la modulación QPSK de secuencias ZC ofrece mayor precisión en condiciones realistas que los otros esquemas de modulación.[Abstract] Many Ultrasonic Local Positioning Systems (U-LPS), consists of multiple fixed beacons that simultaneously emit ultrasonic signals whose times of arrival (ToA) are estimated at a mobile receiver. The ultrasonic signals can be encoded to allow separation of the signals at the receiver, identification of the transmitters, and mitigation of signal impairments such as multipath, the near-far effect, multiple access interference, and Doppler shift. Therefore, waveform design (coding and modulation) constitutes a key factor in determining the performance of such a system. This paper compares by simulation the performance of three modulation techniques (specifically QPSK, OFDM and FHSS) transmitting Zadoff-Chu (ZC) sequences in a U-LPS. Simulation results indicate that ZC coded QPSK modulation with non-coherent detection, offers greater accuracy under realistic conditions than the other modulation schemes.Ministerio de Economía, Industria y Competitividad ; TEC2015-64835-C3-2-RUniversidad de Alcalá; CCGP2017-EXP/05

Optimized correlator for LS codes-based CDMA systems

Loosely Synchronized codes, which have gained considerable interest in CDMA-based wireless communications and sensory systems, can be constructed from a set of mutually orthogonal complementary sets of sequences. In this paper a new architecture is provided for the correlation of such codes. It demands less memory and number of operations than previous ones based on efficient correlators for complementary set of sequences, and can be easily implemented in programmable devices due to its regular structure.Fil: Pérez, Carmen. Universidad de Alcalá; EspañaFil: Ureña, Jesús. Universidad de Alcalá; EspañaFil: Hernández, Álvaro. Universidad de Alcalá; EspañaFil: de Marziani, Carlos Manuel. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: García, J. Jesús. Universidad de Alcalá; EspañaFil: Jiménez, Ana. Universidad de Alcalá; Españ

Doppler-tolerant receiver for an ultrasonic LPS based on Kasami sequences

This paper presents the design of a novel receiver for a broadband ultrasonic Local Positioning System. As other devices based on matched ltering of the transmitted encoded signals, this receiver features high robustness to noise and multiple access capability. Unlike these previous solutions, the proposed receiver is capable to detect the beacons emissions despite being installed in a fast moving user and to provide an estimation of its velocity. This system has been implemented on a FPGA based architecture. An experimental analysis of the sensor performance has been carried out with a set of test signals synthetically generated to simulate diferent positions and velocities for this receiver. The results confirm the capability of the system to detect the encoded signals emitted by the LPS architecture when moving at velocities of up to 3 m/s under low SNR conditions.Fil: Alvarez, Fernando J.. Universidad de Extremadura; EspañaFil: Hernadez, Alvaro. Universidad de Alcala; EspañaFil: Moreno, José A.. Universidad de Extremadura; EspañaFil: Perez, M. Carmen. Universidad de Alcala; EspañaFil: Ureña, Jesus. Universidad de Alcala; EspañaFil: de Marziani, Carlos Manuel. Universidad Nacional de la Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin