Higher order feature extraction and selection for robust human gesture recognition using CSI of COTS Wi-Fi devices

Device-free human gesture recognition (HGR) using commercial o the shelf (COTS) Wi-Fi devices has gained attention with recent advances in wireless technology. HGR recognizes the human activity performed, by capturing the reflections ofWi-Fi signals from moving humans and storing them as raw channel state information (CSI) traces. Existing work on HGR applies noise reduction and transformation to pre-process the raw CSI traces. However, these methods fail to capture the non-Gaussian information in the raw CSI data due to its limitation to deal with linear signal representation alone. The proposed higher order statistics-based recognition (HOS-Re) model extracts higher order statistical (HOS) features from raw CSI traces and selects a robust feature subset for the recognition task. HOS-Re addresses the limitations in the existing methods, by extracting third order cumulant features that maximizes the recognition accuracy. Subsequently, feature selection methods derived from information theory construct a robust and highly informative feature subset, fed as input to the multilevel support vector machine (SVM) classifier in order to measure the performance. The proposed methodology is validated using a public database SignFi, consisting of 276 gestures with 8280 gesture instances, out of which 5520 are from the laboratory and 2760 from the home environment using a 10 5 cross-validation. HOS-Re achieved an average recognition accuracy of 97.84%, 98.26% and 96.34% for the lab, home and lab + home environment respectively. The average recognition accuracy for 150 sign gestures with 7500 instances, collected from five di erent users was 96.23% in the laboratory environment.Taylor's University through its TAYLOR'S PhD SCHOLARSHIP Programmeinfo:eu-repo/semantics/publishedVersio

Doctor of Philosophy

dissertationThis work seeks to improve upon existing methods for device-free localization (DFL) using radio frequency (RF) sensor networks. Device-free localization is the process of determining the location of a target object, typically a person, without the need for a device to be with the object to aid in localization. An RF sensor network measures changes to radio propagation caused by the presence of a person to locate that person. We show how existing methods which use either wideband or narrowband RF channels can be improved in ways including localization accuracy, energy efficiency, and system cost. We also show how wideband and narrowband systems can combine their information to improve localization. A common assumption in ultra-wideband research is that to estimate the bistatic delay or range, "background subtraction" is effective at removing clutter and must first be performed. Another assumption commonly made is that after background subtraction, each individual multipath component caused by a person's presence can be distinguished perfectly. We show that these assumptions are often not true and that ranging can still be performed even when these assumptions are not true. We propose modeling the difference between a current set of channel impulse responses (CIR) and a set of calibration CIRs as a hidden Markov model (HMM) and show the effectiveness of this model over background subtraction. The methods for performing device-free localization by using ultra-wideband (UWB) measurements and by using received signal strength (RSS) measurements are often considered separate topic of research and viewed only in isolation by two different communities of researchers. We consider both of these methods together and propose methods for combining the information obtained from UWB and RSS measurements. We show that using both methods in conjunction is more effective than either method on its own, especially in a setting where radio placement is constrained. It has been shown that for RSS-based DFL, measuring on multiple channels improves localization accuracy. We consider the trade-o s of measuring all radio links on all channels and the energy and latency expense of making the additional measurements required when sampling multiple channels. We also show the benefits of allowing multiple radios to transmit simultaneously, or in parallel, to better measure the available radio links

Spin dynamics near the critical doping in weakly-superconducting underdoped YBa2Cu3O6.35 (Tc=18K)

Using neutron scattering we have determined the magnetic structure and fluctuations in the YBa2Cu3O6.35 superconductor (Tc=18 K). The long-range ordered collinear spins of the insulating antiferromagnet are replaced by a commensurate central mode arising from slow, isotropically polarized, short-range spin correlations. The inelastic spectrum up to 30 meV is broad in wave vector and commensurate. In contrast to the the resonance peak of higher Tc superconductors, the spins exhibit a single overdamped spectrum whose rate of relaxation decreases on cooling and saturates at 5 meV below 50 K. As the relaxation rate saturates the quasi-static spin correlations grow and become resolution limited in energy. The spin susceptibility at high temperatures illustrates that the dominant energy scale is set by the temperature. At low temperatures, the scale length is geometric and not linked by velocity to dynamic widths. There is no observable suppression of the spin fluctuations or central mode upon the onset of superconductivity. The spins respond not to coherent charge pairs but to hole doping allowing coexistence of glassy short range spin order with superconductivity. Since the physics of the weakly superconducting system YBCO6.35 must connect continuously with that in more strongly superconducting YBCO6.5, we find that neither incommensurate stripe-like spin modulations nor a well-defined neutron spin resonance are essential for the onset with doping of pairing in a high temperature cuprate superconductor.Comment: 22 pages, 19 figures, accepted for publication in Phys. Rev.

Design and theoretical analysis of advanced power based positioning in RF system

Accurate locating and tracking of people and resources has become a fundamental requirement for many applications. The global navigation satellite systems (GNSS) is widely used. But its accuracy suffers from signal obstruction by buildings, multipath fading, and disruption due to jamming and spoof. Hence, it is required to supplement GPS with inertial sensors and indoor localization schemes that make use of WiFi APs or beacon nodes. In the GPS-challenging or fault scenario, radio-frequency (RF) infrastructure based localization schemes can be a fallback solution for robust navigation. For the indoor/outdoor transition scenario, we propose hypothesis test based fusion method to integrate multi-modal localization sensors. In the first paper, a ubiquitous tracking using motion and location sensor (UTMLS) is proposed. As a fallback approach, power-based schemes are cost-effective when compared with the existing ToA or AoA schemes. However, traditional power-based positioning methods suffer from low accuracy and are vulnerable to environmental fading. Also, the expected accuracy of power-based localization is not well understood but is needed to derive the hypothesis test for the fusion scheme. Hence, in paper 2-5, we focus on developing more accurate power-based localization schemes. The second paper improves the power-based range estimation accuracy by estimating the LoS component. The ranging error model in fading channel is derived. The third paper introduces the LoS-based positioning method with corresponding theoretical limits and error models. In the fourth and fifth paper, a novel antenna radiation-pattern-aware power-based positioning (ARPAP) system and power contour circle fitting (PCCF) algorithm are proposed to address antenna directivity effect on power-based localization. Overall, a complete LoS signal power based positioning system has been developed that can be included in the fusion scheme --Abstract, page iv

Simultaneous ranging and self-positioning in unsynchronized wireless acoustic sensor networks

Automatic ranging and self-positioning is a very desirable property in wireless acoustic sensor networks (WASNs) where nodes have at least one microphone and one loudspeaker. However, due to environmental noise, interference and multipath effects, audio-based ranging is a challenging task. This paper presents a fast ranging and positioning strategy that makes use of the correlation properties of pseudo-noise (PN) sequences for estimating simultaneously relative time-of-arrivals (TOAs) from multiple acoustic nodes. To this end, a proper test signal design adapted to the acoustic node transducers is proposed. In addition, a novel self-interference reduction method and a peak matching algorithm are introduced, allowing for increased accuracy in indoor environments. Synchronization issues are removed by following a BeepBeep strategy, providing range estimates that are converted to absolute node positions by means of multidimensional scaling (MDS). The proposed approach is evaluated both with simulated and real experiments under different acoustical conditions. The results using a real network of smartphones and laptops confirm the validity of the proposed approach, reaching an average ranging accuracy below 1 centimeter.This work was supported by the Spanish Ministry of Economy and Competitiveness under Grant TIN2015-70202-P, TEC2012-37945-C02-02 and FEDER funds

Sensors and Systems for Indoor Positioning

This reprint is a reprint of the articles that appeared in Sensors' (MDPI) Special Issue on “Sensors and Systems for Indoor Positioning". The published original contributions focused on systems and technologies to enable indoor applications

Development and deployment of a small stereo-hearing testing system: Two manuscripts

MANUSCRIPT #1 TITLE Development of a Deployable Stereo-Hearing System ABSTRACT Objective: To investigate the effectiveness and efficiency of a portable stereo-hearing testing system with the intent of deployment for data collection in future studies. We quantify sound localization accuracy and speech-in-noise thresholds comparing unilateral (such as single-sided deafness) and bilateral subjects. We desired to design a small, inexpensive system that would show a large effect size between binaural and monaural subjects in a variety of stereo hearing tasks. Methods: Subjects were tested on localization accuracy and speech understanding in noise using a laboratory-made stereo-hearing testing device. For the localization task, the subject identifies the location of a 250 ms noise presented randomly at one of 8 speakers in a 180o array. For the speech-in-noise task, the subject identifies the CRM color/number command presented from a speaker in one hemi-field while an adaptive noise track is presented simultaneously from a speaker in the opposite hemi-field. RMS error quantified accuracy of localization. Analysis of the speech-detection thresholds involved differences between conditions when the speech and noise were each on different sides: a best-to-worst condition compared speech toward the good ear and noise toward the bad ear and vice versa; in a good-to-poor condition both the speech and noise were closer to midline (approaching straight ahead of the subject) but still on opposite hemi-fields. The right ear was considered ‘good’ for bilaterally-normal control subjects. We expect a large difference between the ‘best’ and ‘worst’ conditions for unilateral subjects and no such difference for the bilateral controls. Results: Differences exist between unilateral and bilateral subjects in both sound localization and understanding speech in noise with ‘extremely large’ effect sizes (Cohen’s d \u3e3 or ‘huge’ for both tests (and 1.6 or twice what Cohen said was a ‘large effect’ for the ‘good-to-poor’ comparison). Bilateral subjects localized and listened in noise better than unilateral subjects (p Conclusions: Our device can distinguish between monaural and binaural subjects and is ready for deployment to investigate patients after otologic surgery, who we expect to perform ‘between’ these unilateral and bilateral subjects.Bilateral subjects localized sounds with near-perfect accuracy while unilateral subjects made many more errors. In unilateral subjects, thresholds detecting signals in noise were highly dependent on which hemi-fields produced the signal and noise (as expected, participants with unilateral hearing heard better when the signal was on the side of their one normal ear with contralateral noise facing the poorer ear) while bilateral subjects were relatively unaffected by the hemi-field of signal and noise. Plugged subjects (bilateral controls with an ear plug and an earmuff) localized worse than true unilateral subjects, suggesting an effect of learning how to localize with monaural cues. MANUSCRIPT #2 TITLE Deployment of a Stereo-Hearing System to Postoperative Atresia Patients ABSTRACT Objective: To investigate the performance of atresia patients, postoperatively, in two binaural processing tasks, and to compare that performance to subjects with normal hearing and subjects with a complete unilateral hearing loss. To investigate the reliability, validity, and efficiency of collecting data via transcontinental shipment of the prototype device. Methods: From their home, subjects were tested on localization accuracy and speech understanding in noise using a laboratory-made stereo-hearing testing device. For the localization task, the subject identified the location of a 250 ms noise burst presented randomly from an 8-speaker array. For the speech-in-noise task, the subject must identify a color/number command presented from a speaker in one hemi-field while an adaptive noise track is presented simultaneously from a speaker in the adjacent hemi-field. The test is repeated with different locations of speech and noise. Results: Postoperative atresia subjects performed better than unilateral subjects in all tasks, showing the expected improvements in binaural processing following canal-plasty. Atresia patients equaled the bilateral controls in sound localization and the most challenging speech in noise test. Within this initial sample of atresia patients (N=9) only vague trends are evident among the dependent variables and with various covariates. Post-operative audiometric speech reception thresholds correlate with the speech in noise testing. Both localization and speech-in-noise understanding appear to improve over post-operative time as a general trend, but outlier(s) increase the variance to a point of statistical insignificance. Conclusions: Repaired atresia subjects perform better than unilateral subjects in localizing sound and understanding speech with a separated noise. The performance of the post-op atresia patients is closer to the bilateral subjects than to unilateral subjects, confirming a benefit of the surgical repair of congenital conductive hearing loss. Our device can be used reliably and efficiently to collect data via transcontinental shipment to residential locations. More follow-up longitudinal data would help investigate any improvement in of binaural listening tasks over time in these patients. One option to continue this research is for medical centers to deploy this device to patients’ homes annually for updated testing