Dial It In: Rotating RF Sensors to Enhance Radio Tomography

A radio tomographic imaging (RTI) system uses the received signal strength (RSS) measured by RF sensors in a static wireless network to localize people in the deployment area, without having them to carry or wear an electronic device. This paper addresses the fact that small-scale changes in the position and orientation of the antenna of each RF sensor can dramatically affect imaging and localization performance of an RTI system. However, the best placement for a sensor is unknown at the time of deployment. Improving performance in a deployed RTI system requires the deployer to iteratively "guess-and-retest", i.e., pick a sensor to move and then re-run a calibration experiment to determine if the localization performance had improved or degraded. We present an RTI system of servo-nodes, RF sensors equipped with servo motors which autonomously "dial it in", i.e., change position and orientation to optimize the RSS on links of the network. By doing so, the localization accuracy of the RTI system is quickly improved, without requiring any calibration experiment from the deployer. Experiments conducted in three indoor environments demonstrate that the servo-nodes system reduces localization error on average by 32% compared to a standard RTI system composed of static RF sensors.Comment: 9 page

Towards Picogram Detection of Superparamagnetic Iron-Oxide Particles Using a Gradiometric Receive Coil

Superparamagnetic iron-oxide nanoparticles can be used in a variety of medical applications like vascular or targeted imaging. Magnetic particle imaging (MPI) is a promising tomographic imaging technique that allows visualizing the 3D nanoparticle distribution concentration in a non-invasive manner. The two main strengths of MPI are high temporal resolution and high sensitivity. While the first has been proven in the assessment of dynamic processes like cardiac imaging, it is unknown how far the detection limit of MPI can be lowered. Within this work, we will present a highly sensitive gradiometric receive-coil unit combined with a noise-matching network tailored for the measurement of mice. The setup is capable of detecting 5 ng of iron in vitro at 2.14 sec acquisition time. In terms of iron concentration we are able to detect 156 {\mu}g/L marking the lowest value that has been reported for an MPI scanner so far. In vivo MPI mouse images of a 512 ng bolus at 21.5 ms acquisition time allow for capturing the flow of an intravenously injected tracer through the heart of a mouse. Since it has been rather difficult to compare detection limits across MPI publications we propose guidelines improving the comparability of future MPI studies.Comment: 15 Pages, 7 Figures, V2: Changed the initials of Author Kannan M Krishnan, added two citations, corrected typo

HYBRYDOWY SYSTEM NAWIGACJI DO UŻYTKU WEWNĄTRZ POMIESZCZEŃ

This article describes the design and implementation of a hybrid in-building navigation system. The word hybrid has a twofold meaning in this case. On the one hand, it refers to the use of two tracking methods: demanding (beacons) and not requiring an electronic device (radio tomography imaging). On the other hand, it specifies several commercial wireless communication protocols that make up the presented system. Ultimately, the network created in this way will be designed to provide the user with location and navigation services with increased accuracy and reliability. The text describes both the topology of created networks, methods of communication between devices and their hardware layer, as well as the effects of work resulting from the actual test object.Artykuł opisuje projekt i sposób realizacji hybrydowego systemu nawigacji wewnątrzbudynkowej. Słowo hybrydowy ma w tym przypadku dwojakie znaczenie. Z jednej strony odnosi się do zastosowania dwóch metod namierzania: wymagającej (radiolatarnie) i nie wymagającej posiadania urządzenia elektronicznego (obrazowanie radio-tomograficzne). Z drugiej wyszczególnia kilka komercyjnych protokołów komunikacji bezprzewodowej składającej się na przedstawiony system. Docelowo utworzone w ten sposób sieć będzie miała za zadanie świadczyć użytkownikowi usługi lokalizacyjne i nawigacyjne o zwiększonej dokładności i niezawodności. Treść tekstu opisuje zarówno topologię tworzonych sieci, metody komunikacji między urządzeniami oraz ich warstwę sprzętową jak i efekty prac wynikłych na podstawie rzeczywistego obiektu testowego

Doctor of Philosophy

dissertationLow-cost wireless embedded systems can make radio channel measurements for the purposes of radio localization, synchronization, and breathing monitoring. Most of those systems measure the radio channel via the received signal strength indicator (RSSI), which is widely available on inexpensive radio transceivers. However, the use of standard RSSI imposes multiple limitations on the accuracy and reliability of such systems; moreover, higher accuracy is only accessible with very high-cost systems, both in bandwidth and device costs. On the other hand, wireless devices also rely on synchronized notion of time to coordinate tasks (transmit, receive, sleep, etc.), especially in time-based localization systems. Existing solutions use multiple message exchanges to estimate time offset and clock skew, which further increases channel utilization. In this dissertation, the design of the systems that use RSSI for device-free localization, device-based localization, and breathing monitoring applications are evaluated. Next, the design and evaluation of novel wireless embedded systems are introduced to enable more fine-grained radio signal measurements to the application. I design and study the effect of increasing the resolution of RSSI beyond the typical 1 dB step size, which is the current standard, with a couple of example applications: breathing monitoring and gesture recognition. Lastly, the Stitch architecture is then proposed to allow the frequency and time synchronization of multiple nodes' clocks. The prototype platform, Chronos, implements radio frequency synchronization (RFS), which accesses complex baseband samples from a low-power low-cost narrowband radio, estimates the carrier frequency offset, and iteratively drives the difference between two nodes' main local oscillators (LO) to less than 3 parts per billion (ppb). An optimized time synchronization and ranging protocols (EffToF) is designed and implemented to achieve the same timing accuracy as the state-of-the-art but with 59% less utilization of the UWB channel. Based on this dissertation, I could foresee Stitch and RFS further improving the robustness of communications infrastructure to GPS jamming, allow exploration of applications such as distributed beamforming and MIMO, and enable new highly-synchronous wireless sensing and actuation systems

Wireless sensor systems in indoor situation modeling II (WISM II)

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Comparison of Methods for Radio Position of Non-Emitting Dismounts

Radio Tomographic Imaging (RTI) is a form of Device Free Passive Localization (DFPL) that utilizes the Received Signal Strength (RSS) values from a collection of wireless transceivers to produce an image in order to localize a subject within a Wireless Sensor Network (WSN). Radio Mapping is another form of DFPL that can utilize the same RSS values from a WSN to localize a subject by comparing recent values to a set of calibration data. RTI and Radio Mapping have never been directly compared to one another as a means of localization within a WSN. The goal of this research is to compare using TelosB mote devices these approaches in a side-by-side manner. A real world WSN was constructed and both RTI and Radio Mapping methodologies were applied to identical data sets with the results compared and discussed. Initial results show that both methodologies have inherent advantages and disadvantages respective to one another; Radio Mapping performs significantly better in WSNs with a low number of transceivers being 100% accurate within the bounds of this experimentation, while RTI has significantly more simple calibration procedures

OPTYMALIZACJA PROCESÓW ZARZĄDZANIA BUDYNKAMI KOMERCYJNYMI Z WYKORZYSTANIEM SYSTEMÓW ANALIZY ZACHOWAŃ UŻYTKOWNIKÓW WSPOMAGANYCH INTELIGENCJĄ OBLICZENIOWĄ I RTI

The aim of the presented project was to create a comprehensive building management system equipped with a network of wireless and energy-efficient sensors that collect data about users and on their basis control final devices such as lighting, ventilation, air conditioning and heating. In the presented system, end devices can be both products offered by the market (commercial) and proprietary solutions (own). This is to allow the adaptation of commercial radio communication protocols with high integration capabilities and common occurrence. In addition, the system has been enriched with an innovative system of tracking and building navigation and access control, which are supported by a network of radio beacons and radio-tomographic imaging technology (RTI). The whole system is to be supervised by computational intelligence learned from scratch.Celem prezentowanego projektu było stworzenie kompleksowego systemu zarządzania budynkiem wyposażonego w sieć bezprzewodowych i energooszczędnych czujników, które zbierają dane o użytkownikach i na ich podstawie sterują urządzeniami końcowymi, takimi jak oświetlenie, wentylacja, klimatyzacja i ogrzewanie. W prezentowanym systemie urządzeniami końcowymi mogą być zarówno produkty oferowane przez rynek (komercyjne), jak i rozwiązania autorskie (własne). Ma to na celu umożliwienie adaptacji komercyjnych protokołów komunikacji radiowej o dużych możliwościach integracyjnych i powszechnym występowaniu. Dodatkowo system został wzbogacony o innowacyjny system śledzenia i nawigacji po budynkach oraz kontroli dostępu, które są wspomagane przez sieć radiolatarni oraz technologię obrazowania radiowo-tomograficznego (RTI). Nad całością systemu ma czuwać inteligencja obliczeniowa wyuczona od podstaw

Radio Tomographic Imaging using a Modified Maximum Likelihood Estimator for Image Reconstruction in Various Environments

Radio Tomographic Imaging (RTI) is an emerging Device-Free Passive Localization (DFPL) technology. Radio Tomographic Imaging (RTI) involves using a set of small low cost wireless transceivers to create a Wireless Sensor Network (WSN) around an Area of Interest (AoI). Furthermore, the Received Signal Strength (RSS) between transceiver pairs is utilized to reconstruct an image from the signal attenuation caused by an object disrupting the links. This image can then be utilized for multiple applications ranging from localization to target detection and tracking. This enhances the importance of image resolution in order to capture the actual size of the objects as well as the ability to resolve multiple objects in an AoI. The objective of this research is to propose a new image formation technique for a reconstructed image within aWSN. This was accomplished using a modified Maximum Likelihood Estimate (MLE) function that forces the desired solution to be positive. Other regularization techniques must implement different methods to mitigate the undesired singular values caused from a non-invertible matrix. Additionally, the research highlights the performance of the modified MLE estimator and the robustness of improved image resolution in three different environments