High-rate UWB and 60 GHz communications

In this chapter, two technologies for high data-rate communications systems for wireless personal area networks (WPANs) are discussed. Namely, the ultrawideband (UWB) technology that operates in the 3.1-10.6 GHz band and the millimeter wave (MMW) technology (also called 60 GHz radio) that can use the 57-64 GHz band in most parts of the world are considered. First, a generic overview is given and various application scenarios are discussed. Then, the ECMA standard for high-rate UWB systems is studied. Finally, two standards for the 60 GHz MMW radio are investigated.Overview and application scenarios In order to realize high-speed communications systems with low power consumption, signals with very large bandwidths need to be employed. One way of designing such communications systems is to use UWB signals as an underlay technology by utilizing all or part of the frequency spectrum between 3.1 and 10.6 GHz [1-3]. According to the US Federal Communications Commission (FCC), a UWB signal is defined as having an absolute bandwidth of at least 500 MHz or a relative (fractional) bandwidth of larger than 20% [3-4].In order not to cause any adverse effects on other wireless systems in the same frequency band, such as IEEE 802.11a wireless local area networks (WLANs), certain power emission limits are imposed on UWB devices by regulatory authorities, such as the FCC in the USA [3] and the Electronic Communications Committee (ECC) in Europe [5]. © Cambridge University Press 2011

Will a Fixed Price Reimbursement Policy for Statins be Cost-Effective for Turkey's Health Care System?

Type: Commentar

Will Translational Science Help Reduce Costs of Illness?

The purpose of this commentary is to (1) review the definition and potential benefits of translational science research, (2) comment on funding trends for translational science, (3) pose a question for scientists to discuss, and (4) propose recommendations for such a discussion. Type: Commentar

CBRS Spectrum Sharing between LTE-U and WiFi: A Multiarmed Bandit Approach

The surge of mobile devices such as smartphone and tablets requires additional capacity. To achieve ubiquitous and high data rate Internet connectivity, effective spectrum sharing and utilization of the wireless spectrum carry critical importance. In this paper, we consider the use of unlicensed LTE (LTE-U) technology in the 3.5 GHz Citizens Broadband Radio Service (CBRS) band and develop a multiarmed bandit (MAB) based spectrum sharing technique for a smooth coexistence with WiFi. In particular, we consider LTE-U to operate as a General Authorized Access (GAA) user; hereby MAB is used to adaptively optimize the transmission duty cycle of LTE-U transmissions. Additionally, we incorporate downlink power control which yields a high energy efficiency and interference suppression. Simulation results demonstrate a significant improvement in the aggregate capacity (approximately 33%) and cell-edge throughput of coexisting LTE-U and WiFi networks for different base station densities and user densities

Fundamental limits and improved algorithms for linear least-squares wireless position estimation

In this paper, theoretical lower bounds on performance of linear least-squares (LLS) position estimators are obtained, and performance differences between LLS and nonlinear least-squares (NLS) position estimators are quantified. In addition, two techniques are proposed in order to improve the performance of the LLS approach. First, a reference selection algorithm is proposed to optimally select the measurement that is used for linearizing the other measurements in an LLS estimator. Then, a maximum likelihood approach is proposed, which takes correlations between different measurements into account in order to reduce average position estimation errors. Simulations are performed to evaluate the theoretical limits and to compare performance of various LLS estimators. Copyright © 2010 John Wiley & Sons, Ltd

On the performance of linear least-squares estimation in wireless positioning systems

A common technique for wireless positioning is to estimate time-of-arrivals (TOAs) of signals traveling between a target node and a number of reference nodes, and then to determine the position of the target node based on those TOA parameters. In determining the position of the target node from TOA parameters, linear or nonlinear least-squares (LS) estimation techniques can be employed. Although the linear LS techniques are suboptimal in general, they facilitate low-complexity position estimation. In this paper, performance of various linear LS techniques are compared, and suboptimality of the linear approach is quantified in terms of the Cramer-Rao lower bound (CRLB). Simulations are performed to compare the performance of the linear LS approaches versus the CRLBs for linear and nonlinear techniques. ©2008 IEEE

Ultra-wideband range estimation: Theoretical limits and practical algorithms

The high time resolution of ultra-wideband (UWB) signals enables wireless devices to perform accurate range estimation. In order to realize UWB systems with accurate ranging capabilities, both theoretical limits on range estimation and practical algorithms that approach those limits should be investigated. This paper provides a survey of various UWB ranging algorithms and discusses their performance and complexity tradeoffs. In addition, theoretical limits on range estimation are discussed in terms of Cramer-Rao and Ziv-Zakai lower bounds. Index Terms- Ultra-wideband (UWB), time-of-arrival (TOA) estimation, ranging, Cramer-Rao lower bound (CRLB), Ziv-Zakai lower bound (ZZLB). ©2008 IEEE

Agricultural Academy

Abstract KAYMAK, H. C., I. GUVENC and A. GUROL, 2010. Elemental analysis of different radish (Raphanus sativus L.) Cultivars by using wavelength-dispersive X-ray fluorescence spectrometry (WDXRF). Bulg. J. Agric. Sci., The aim of this work is to study the applicability of a quantitative WDXRF (Wavelength-Dispersive X-ray Fluorescence) method, for determination of minerals in radish specimens. In this study, we have quantitatively and semi-quantitatively analysed the four different radish (Raphanus sativus L.) cultivars (cvs. 'Siyah', 'Beyaz', 'Antep' and 'Iri-Kirimizi'). We have found that major elements; namely N and K; a few minor elements; Na, Mg, P, S, and Ca, and a lot of trace elements; Mn, Fe, Cu, Zn, Al, Ti, Cr, Br, Rb, Sr, Sn, Ba and La. The obtained trace element concentrations range from 0.01 to 3.24 mg per 100 g. This rapid method has been found to be a reliable technique for analyzing the mineral content in radish. At the end of this work, it was clearly said that Wavelengthdispersive X-ray fluorescence spectrometry (WDXRF) could be used for the analysis of mineral contents of radish and other vegetables