Evaluation of a geometric positioning algorithm for hybrid wireless networks

International audienceIn this paper, we propose a geometric positioning method for hybrid wireless networks, based on a set membership method. Three common types of radio observables are considered for the position estimation: range, difference of ranges and received power. This paper details how to build geometric constraints from observables, and how to merge them to estimate the position. Given a realistic scenario, Monte Carlo simulation shows that the performance of the proposed method in terms of root mean squared error and cumulative density functions outperforms that of a numerically optimized maximum likelihood

Improved Mobility Modeling for Indoor Localization Applications

International audienceThis paper presents a novel mobility model to perform realistic simulations of human movements and behaviors. The proposed model is based on discrete event simulation and graph theory. The proposed model is implemented in a wireless propagation simulator and used to evaluate various wireless network protocols including: propagation, localization and communication

PyLayers: An open source dynamic simulator for indoor propagation and localization

International audience— In this paper, we introduce PyLayers a new open source radio simulator built to tackle indoor localization problem. PyLayers has been designed to simulate complete dynamic scenarios including the realistic movement of persons inside a building, the transmission channel estimation for multiple radio access technologies and the position estimation relying on location-dependent parameters originated from the simulated OSI physical layer. The channel is estimated by using a fast graph-based ray tracing method. From these simulated data, location dependent parameters, such as received power or time of arrival, can be deduced. The realistic movement of persons into the building layout is modeled with a virtual forces approach. The simulated data can be directly used with one of the built-in localization algorithms or be exported to various standards extensions. Finally, the accuracies of both the channel estimation and the localization are compared to measurements and show a good match

Evaluation of a geometric positioning algorithm for hybrid wireless networks

International audienceIn this paper, we propose a geometric positioning method for hybrid wireless networks, based on a set membership method. Three common types of radio observables are considered for the position estimation: range, difference of ranges and received power. This paper details how to build geometric constraints from observables, and how to merge them to estimate the position. Given a realistic scenario, Monte Carlo simulation shows that the performance of the proposed method in terms of root mean squared error and cumulative density functions outperforms that of a numerically optimized maximum likelihood

Biology of the immunomodulatory molecule HLA-G in human liver diseases.

International audienceThe non-classical human leukocyte antigen-G, HLA-G, plays an important role in inducing tolerance, through its immunosuppressive effects on all types of immune cells. Immune tolerance is a key issue in the liver, both in liver homeostasis and in the response to liver injury or cancer. It would therefore appear likely that HLA-G plays an important role in liver diseases. Indeed, this molecule was recently shown to be produced by mast cells in the livers of patients infected with hepatitis C virus (HCV). Furthermore, the number of HLA-G-positive mast cells was significantly associated with fibrosis progression. The generation of immune tolerance is a role common to both HLA-G, as a molecule, and the liver, as an organ. This review provides a summary of the evidence implicating HLA-G in liver diseases. In the normal liver, HLA-G transcripts can be detected, but there is no HLA-G protein. However, HLA-G protein is detectable in the liver tissues and/or plasma of patients suffering from hepatocellular carcinoma, hepatitis B or C, or visceral leishmaniasis and in liver transplant recipients. The cells responsible for producing HLA-G differ between diseases. HLA-G expression is probably induced by microenvironmental factors, such as cytokines. The expression of HLA-G receptors, such as ILT2, ILT4, and KIRD2L4, on liver cells has yet to be investigated, but these receptors have been detected on all types of immune cells, and such cells are present in liver. The tolerogenic properties of HLA-G explain its deleterious effects in cancers and its beneficial effects in transplantation. Given the key role of HLA-G in immune tolerance, new therapeutic agents targeting HLA-G could be tested for the treatment of these diseases in the future

Exploiting the Graph Description of Indoor Layout for Ray Persistency Modeling in Moving Channel

International audienceThis paper proposes a technique based on descrip- tion of the layout using different graphs to obtain a ray signature which is associated with path persistency observed for small displacement of radio link termination of a mobile channel. The algorithm used to derive the signature from the layout graph description and the position of Tx and Rx is described. The mathematical relationship between signature and rays is also presented. A comparison of simulated and measured IR-UWB channel impulse response over a pedestrian trajectory is shown

WBAN Off-Body Channel Angular Structure Comparison between SAGE Estimation and Ray Tracing Simulation

International audienceIn this paper, we present a comparison between Off-Body channel characteristics estimated with Space-Alternating Generalized Expectation-Maximization (SAGE) algorithm from measurement data and those obtained from ray-tracing simulated data. Measurement data were obtained considering a body-worn antenna on a phantom and an external one simulating an access point. The chosen simulation approach takes into account the influence of the body directly into the antenna radiation pattern, and not by including a dedicated body representation into the simulated environment. This simplified approach provides a good agreement between simulation and measurement in terms of received power and Angle of Arrival retrieval

A Hybrid Positioning Method Based on Hypothesis Testing

International audienceWe consider positioning in the scenario where only two reliable range estimates, and few less reliable power observations are available. Such situations are difficult to handle with numerical maximum likelihood methods which require a very accurate initialization to avoid being stuck into local maxima. We propose to first estimate the support region of the two peaks of the likelihood function using a set membership method, and then decide between the two regions using a rule based on the less reliable observations. Monte Carlo simulations show that the performance of the proposed method in terms of outlier rate and root mean squared error approaches that of maximum likelihood when only few additional power observations are available

Tetranucleotides as a scaffold for diporphyrin arrays

The incorporation of porphyrin-substituted nucleosides into tetranucleotides using phosphoramidite chemistry on solid support is reported. Both diphenyl and tetraphenyl porphyrin nucleosides were used as building blocks. This method allows the synthesis of chiral homo- and heteroporphyrinic arrays, where the composition and thus the physical properties of the array can be modulated simply by reprogramming the DNA synthesizer. The porphyrin arrays are initially isolated in the free-base form. Remetallation to give the zinc-porphyrins can be achieved using standard procedures in solution. The UV-vis spectra of the arrays are reproducible by a superposition of the absorbance spectra of the individual porphyrins, indicating an undisturbed electronic ground state of the porphyrins in the arrays. The same is true for the steady-state emission spectra of the homoporphyrinic arrays, which are not influenced by the presence of the nucleotide strand. In the mixed porphyrin arrays, large differences in the excited-state properties compared to an equimolar mixture of the building blocks are observed by means that the emission of the diphenyl porphyrin moiety is quenched to a large extent, and the overall emission is dominated by the tetraphenyl porphyrin. The covalent connection of the porphyrins via the DNA-derived backbone therefore substantially alters the excited-state and energy-transfer properties of mixed porphyrin systems. The circular dichroism (CD) spectra show induced negative cotton effects in the region of the porphyrin B-band absorption, which is due to the attachment of the chromophores to the chiral oligonucleotide backbone. Addition of a complementary tetra-adenosine did not alter any of the spectroscopic properties, neither in chloroform nor in acetonitrile solutions. Therefore, it can be concluded that no duplex is formed, which is corroborated by 1H NMR spectroscop

Localization and Fingerprint of Radio Signals Employing a Multichannel Photonic Analog-to-Digital Converter

[EN] The fingerprint and localization of radio signals employing a multichannel photonic analog-to-digital converter (ADC) is proposed, analyzed, and demonstrated in a laboratory experiment. The photonic ADC detects the radio signals with high sensitivity in a large bandwidth without down-conversion stages. This is of special interest when processing emerging low-power wireless standards like ultra-wideband (UWB) radio. The optical processing in the multichannel photonic ADC is tailored for the localization and fingerprint of generic radio transmitters when orthogonal-frequency division multiplexing (OFDM) modulation is employed in the transmission. The photonic ADC includes engineered optical and electrical amplification. The experimental work demonstrates that detection of radio signals with -65 dBm power with signal-to-noise ratio better than 20 dB is feasible, which is in good accordance with the theoretical analysis. The multichannel photonic ADC comprises five optical channels which are precisely time-aligned in optical domain achieving 0.23-m spatial resolution (median) in the localization of radio transmitters. The experimental work also demonstrates that photonic-ADC processing is adequate for OFDM-based UWB radio-signal fingerprint including estimation of the average power, frequency band of operation, and time-frequency hopping pattern if applicable. UWB transmitter localization has been experimentally demonstrated with 0.4-m error.This work was supported in part by the European 7th Framework Program Project UCELLS FP7-IST-216785. The work of M. Morant was supported by Spain FPU MEC under Grant AP2007-01413.Llorente, R.; Morant, M.; Puche, JF.; Romme, J.; Amiot, N.; Uguen, B.; Duplicy, J. (2010). Localization and Fingerprint of Radio Signals Employing a Multichannel Photonic Analog-to-Digital Converter. IEEE Transactions on Microwave Theory and Techniques. 58(11):3304-3311. https://doi.org/10.1109/TMTT.2010.2076730S33043311581