Acoustical Ranging Techniques in Embedded Wireless Sensor Networked Devices

Location sensing provides endless opportunities for a wide range of applications in GPS-obstructed environments; where, typically, there is a need for higher degree of accuracy. In this article, we focus on robust range estimation, an important prerequisite for fine-grained localization. Motivated by the promise of acoustic in delivering high ranging accuracy, we present the design, implementation and evaluation of acoustic (both ultrasound and audible) ranging systems.We distill the limitations of acoustic ranging; and present efficient signal designs and detection algorithms to overcome the challenges of coverage, range, accuracy/resolution, tolerance to Doppler’s effect, and audible intensity. We evaluate our proposed techniques experimentally on TWEET, a low-power platform purpose-built for acoustic ranging applications. Our experiments demonstrate an operational range of 20 m (outdoor) and an average accuracy 2 cm in the ultrasound domain. Finally, we present the design of an audible-range acoustic tracking service that encompasses the benefits of a near-inaudible acoustic broadband chirp and approximately two times increase in Doppler tolerance to achieve better performance

Analysis and Simulation of MRC Diversity Reception in Correlated Composite Nakagami-Lognormal Fading Channels

The physical meaning of the composite Nakagami-lognormal fading model is not well understood by many researchers using the model. The signal power transfer and transform at the interface between the global lognormal shadowing sub-channels and the local Nakagami multipath sub-channels in the presence of correlation between these diversity sub-channels is rather complex. This is the main reason why a thorough analysis or a simulation model is absent to date for the case of correlated composite Nakagami-lognormal diversity channels. This paper presents a novel technique for the estimation of the probability density function (PDF) of the signal-to-noise (SNR) at the output of a maximum ratio combining (MRC) receiver operating in correlated composite diversity fading channels. The PDF is estimated using the recently proposed two-point lossless moment generating function (MGF) matching technique and a closed-form expression for the bit-error rate (BER) for QPSK signal is consequently presented using the Gauss-Hermite polynomial approximation. The paper also presents the complex Monte-Carlo simulation model for the MRC reception and BER counting in correlated composite Nakagami-lognormal fading channels

Blind equalization and fading channel signal recovery of OFDM modulation

Algorithms for blind equalization and data recovery of orthogonal frequency-division multiplexed (OFDM) signals transmitted through fading channels are implemented and simulated in this thesis. The channel is estimated without knowledge of the transmitted sequence (i.e., blindly) using a least mean squares (LMS) adaptive filter and filter bank precoders. This method was used to estimate channel characteristics using both binary and quadrature phase-shift keying signals. Additionally, the method was analyzed for robustness with a poor initial estimate of channel characteristics, with the addition of white Gaussian noise to the signal, and with non-stationary channel conditions. In addition, it is shown that the proposed method is particularly suited in situations with deep fading channels, where some of the subcarriers have a very low SNR. Simulations for both aspects of this thesis were conducted using MATLAB, and the results are presented.http://archive.org/details/blindequalizatio109455740Approved for public release; distribution is unlimited

Realistic chipless RFID: identification and localization

Für die weitere Massenverbreitung von RFID Systemen ist ein günstiges und genaues Verfahren zur Objektlokalisierung und –verfolgung zwingend erforderlich. Chiplose RFID Systeme erlauben im Gegensatz zu herkömmlichen chipbehafteten RFID Systemen den Einsatz von einfachen, druckbaren RFID Tags, eine Möglichkeit zum Einstieg in die Ära von extrem billigen RFID Tags. Diese Dissertation konzentriert sich auf die Lösung von drei Herausforderungen bei der Erkennung von chiplosen RFID Tags innerhalb geschlossener Räume. Der erste in der vorliegenden Arbeit diskutierte Aspekt beschäftigt sich mit Methoden zum Eliminieren des Störechos der Umgebung (clutter removal techniques). Im chiplosen RFID System ist das Umgebungsstörecho definiert durch das von der Umgebung reflektierte Signal, das nicht mit dem RFID Tag interagiert. Die Stärke dieses Signals ist in jedem Fall größer als die des vom RFID Tag zurückgestrahlten (backscattered) Signals, was die Signaturerkennung des RFID Tags unmöglich macht. Zur Lösung dieses Problems schlage ich zwei Algorithmen vor. Der erste ist die Leerraum-Kalibrierung (empty room calibration). Bei diesem Algorithmus werden die Messungen mit RFID Tag von denen ohne RFID Tags abgezogen. Der zweite Algorithmus basiert auf dem Rake-Receiver unter Nutzung einer Zufallsfolge (PN sequence), er erfordert keine zusätzliche Kalibrierung. Der zweite Aspekt betrifft die Notch Erkennung und Identifikation, ein sehr wichtiger Bereich des chiplosen RFID Systems. Er ist dafür verantwortlich, die Notchs in Bits umzuwandeln. Für eine effektive Detektion werden Windowing (Fenster) Verfahren vorgeschlagen, wobei jedes Fenster einen oder auch keinen Notch beinhalten kann. Insgesamt drei neue Verfahren zur Notch Erkennung wurden implementiert. Als erstes ein Matched Filter (MF), in dem der einkommende Notch mit einem Referenz Notch verglichen wird. Das zweite Verfahren basiert auf einer gefensterten Singulärwertzerlegung, damit kann sowohl der Notch erkannt werden, als auch seine Bandbreite bestimmt werden. Als drittes Verfahren wird das dynamische Frequency Warping vorgestellt. Diese Technik nutzt nichtlineare um die Notche unddie Frequenzverschiebungen, die an den Notches auftreten, zu erkennen. Als dritter Aspekt wird die Lokalisierung der RFID Tags in dieser Dissertation diskutiert. Dazu werden zwei Algorithmen erklärt und implementiert. Der erste Algorithmus beruht auf der Triangulation durch drei getrennte RFID Lesegeräte, während sich der zweite die Position des RFID Tags aus der Signalstärke und dem Winkel des vom RFID Tag kommenden Signals berechnet. Alle genannten Algorithmen und Verfahren wurden in einer realen Innenraum Testumgebung mit RFID Tags und einer Software Defined Radio (SDR) Plattform vermessen, um die Zuverlässigkeit der Algorithmen unter normalen Bedingungen zu überprüfen.For mass deployment of RFID systems, cheap and accurate item level identification and tracking are profoundly needed. Fortunately, unlike conventional chip-based RFID, chipless RFID systems offers low-cost printable tags holding a better chance to enter the era of penny-cost tags. This dissertation concentrated on solving three challenges in the detection of the chipless tag inside an indoor environment. The first aspect discussed in the thesis are the chipless RFID clutter removal techniques. In chipless RFID the environmental clutter response is defined as the signal reflected from the environment, that does not interact with the tag. This signal has higher power than the backscattered signal from the tag, rendering the tag signature undetectable. Two algorithms to overcome this problem was used, the first is empty room calibration. The first algorithm is based on subtracting the measurement with the tag from the one without. The second algorithm is Rake receiver using PN sequence; this algorithm requires no pre-measurement calibration. The second aspect is notch detection and identification which is a critical part of the chipless system. This part is responsible for converting the notches into bits. For effective detection, a windowing operation is proposed, where each window may contain a notch or not. Three novel techniques are implemented to detect the notch. The first is matched filter were a reference notch is compared with the incoming signal. The second is window based singular value decomposition, where a constellation is created to detect not only the existence of a notch but also the bandwidth of the notch. The third notch detection technique is dynamic frequency warping. This technique utilizes non-linear warping to detect the notch and the frequency shifts that occurs on the notch. The third aspect discussed in the thesis is tag localization. In this aspect, two algorithms are implemented and explained. The first is trilateration which requires three different readers. The second localization algorithm exploits received signal strength and angle of arrival to detect the location of the tag accurately. All the algorithms were tested using a real testbed to validate the reliability of the techniques. The measurements were done using fabricated tags in an indoor environment using Software Defines Radio (SDR)

Blind deconvolution of sparse pulse sequences under a minimum distance constraint: a partially collapsed Gibbs sampler method

For blind deconvolution of an unknown sparse sequence convolved with an unknown pulse, a powerful Bayesian method employs the Gibbs sampler in combination with a Bernoulli–Gaussian prior modeling sparsity. In this paper, we extend this method by introducing a minimum distance constraint for the pulses in the sequence. This is physically relevant in applications including layer detection, medical imaging, seismology, and multipath parameter estimation. We propose a Bayesian method for blind deconvolution that is based on a modified Bernoulli–Gaussian prior including a minimum distance constraint factor. The core of our method is a partially collapsed Gibbs sampler (PCGS) that tolerates and even exploits the strong local dependencies introduced by the minimum distance constraint. Simulation results demonstrate significant performance gains compared to a recently proposed PCGS. The main advantages of the minimum distance constraint are a substantial reduction of computational complexity and of the number of spurious components in the deconvolution result

Independent component analysis applications in CDMA systems

Thesis (Master)--Izmir Institute of Technology, Electronics and Communication Engineering, Izmir, 2004Includes bibliographical references (leaves: 56)Text in English; Abstract: Turkish and Englishxi, 96 leavesBlind source separation (BSS) methods, independent component analysis (ICA) and independent factor analysis (IFA) are used for detecting the signal coming to a mobile user which is subject to multiple access interference in a CDMA downlink communication. When CDMA models are studied for different channel characteristics, it is seen that they are similar with BSS/ICA models. It is also showed that if ICA is applied to these CDMA models, desired user.s signal can be estimated successfully without channel information and other users. code sequences. ICA detector is compared with matched filter detector and other conventional detectors using simulation results and it is seen that ICA has some advantages over the other methods.The other BSS method, IFA is applied to basic CDMA downlink model. Since IFA has some convergence and speed problems when the number of sources is large, firstly basic CDMA model with ideal channel assumption is used in IFA application.With simulation of ideal CDMA channel, IFA is compared with ICA and matched filter.Furthermore, Pearson System-based ICA (PS-ICA) method is used forestimating non-Gaussian multipath fading channel coefficients. Considering some fading channel measurements showing that the fading channel coefficients may have an impulsive nature, these coefficients are modeled with an -stable distribution whose shape parameter takes values close to 2 which makes the distributions slightly impulsive. Simulation results are obtained to compare PS-ICA with classical ICA.Also IFA is applied to the single path CDMA downlink model to estimate fading channel by using the advantage of IFA which is the capability to estimate sources with wide class of distributions

Studies on DOA estimation in the presence of multipath in a frequency hopping system

Master'sMASTER OF ENGINEERIN