Accurate Positioning in Ultra-Wideband Systems

Cataloged from PDF version of article.Accurate positioning systems can be realized via ultra-wideband signals due to their high time resolution. In this article, position estimation is studied for UWB systems. After a brief introduction to UWB signals and their positioning applications, two-step positioning systems are investigated from a UWB perspective. It is observed that time-based positioning is well suited for UWB systems. Then time-based UWB ranging is studied in detail, and the main challenges, theoretical limits, and range estimation algorithms are presented. Performance of some practical time-based ranging algorithms is investigated and compared against the maximum likelihood estimator and the theoretical limits. The trade-off between complexity and accuracy is .observe

Optimal Stochastic Parameter Design for Estimation Problems

Cataloged from PDF version of article.In this study, the aim is to perform optimal stochastic parameter design in order to minimize the cost of a given estimator. Optimal probability distributions of signals corresponding to different parameters are obtained in the presence and absence of an average power constraint. It is shown that the optimal parameter design results in either a deterministic signal or a randomization between two different signal levels. In addition, sufficient conditions are obtained to specify the cases in which improvements over the deterministic parameter design can or cannot be achieved via the stochastic parameter design. Numerical examples are presented in order to provide illustrations of theoretical results

Photovoltaic nanocrystal scintillators hybridized on Si solar cells for enhanced conversion efficiency in UV

Cataloged from PDF version of article.We propose and demonstrate semiconductor nanocrystal based photovoltaic scintillators integrated on solar cells to enhance photovoltaic device parameters including spectral responsivity, open circuit voltage, short circuit current, fill factor, and solar conversion efficiency in the ultraviolet. Hybridizing (CdSe) ZnS core-shell quantum dots of 2.4 nm in diameter on multi-crystalline Si solar cells for the first time, we show that the solar conversion efficiency is enhanced 2 folds under white light illumination similar to the solar spectrum. Such nanocrystal scintillators provide the ability to extend the photovoltaic activity towards UV. (c) 2008 Optical Society of America

Optimal stochastic parameter design for estimation problems

In this study, the aim is to perform optimal stochastic parameter design in order to minimize the cost of a given estimator. Optimal probability distributions of signals corresponding to different parameters are obtained in the presence and absence of an average power constraint. It is shown that the optimal parameter design results in either a deterministic signal or a randomization between two different signal levels. In addition, sufficient conditions are obtained to specify the cases in which improvements over the deterministic parameter design can or cannot be achieved via the stochastic parameter design. Numerical examples are presented in order to provide illustrations of theoretical results. © 1991-2012 IEEE

Localized plasmon-engineered spontaneous emission of CdSe/ZnS nanocrystals closely-packed in the proximity of Ag nanoisland films for controlling emission linewidth, peak, and intensity

Cataloged from PDF version of article.Using metallic nanoislands, we demonstrate the localized plasmonic control and modification of the spontaneous emission from closely-packed nanocrystal emitters, leading to significant changes in their collective emission characteristics tuned spectrally and spatially by plasmon coupling. Using randomly-distributed silver nanoislands, we show that the emission linewidth of proximal CdSe/ZnS core-shell quantum dots is reduced by 22% and their peak emission wavelength is shifted by 14nm, while their ensemble photoluminescence is enhanced via radiative energy transfer by 21.6 and 15.1 times compared to the control groups of CdSe/ZnS nanocrystals with identical nano-silver but no dielectric spacer and the same nanocrystals alone, respectively. (C) 2007 Optical Society of America

Enhancements to threshold based range estimation for ultra-wideband systems

Ultra-wideband (UWB) signals have very high time resolution, which makes them a very good candidate for range estimation based wireless positioning. Although the accuracy is the major concern for range estimation, it is also important to have low-complexity algorithms that can be employed in real time. In this study, two low-complexity range estimation algorithms are proposed for UWB signals, which achieve improved performance compared to the state-of-the-art low-complexity ranging algorithms. The proposed algorithms are inspired from two well-known algorithms; 'serial backward search' (SBS) and 'jump back and search forward' (JBSF). Performances of the proposed algorithms are compared with those of the SBS and JBSF algorithms based on real measurements. In addition, theoretical bounds are calculated in order to quantify the statistical performance of the algorithms. © 2014 IEEE

CdSe/ZnS core-shell nanocrystal based scintillators for enhanced detection in UV

[No abstract available

Nanocrystal emitters for enhanced photovoltaics in UV

[No abstract available

Localized plasmon-engineered spontaneous emission of CdSe/ZnS nanocrystals closely-packed in the proximity of Ag nanoislands

[No abstract available

Photonic devices and systems embedded with nanocyrstals

We review our research work on the development of photonic devices and systems embedded with nanocyrstals for new functionality within EU Phoremost Network of Excellence on nanophotonics. Here we report on CdSe/ZnS nanocrystalbased hybrid optoelectronic devices and systems used for scintillation to enhance optical detection and imaging in the ultraviolet range and for optical modulation via electric field dependent optical absorption and photoluminescence in the visible. In our collaboration with DYO, we also present photocatalytic TiO2 nanoparticles incorporated in solgel matrix that are optically activated in the ultraviolet for the purpose of self-cleaning