Compensation of non-reciprocal interference in adaptive MIMO-OFDM cellular systems

In a time-division-duplex communication system, the channel knowledge can be obtained at the transmitter side due to channel reciprocity and it can be used to increase the spectral efficiency of a multiple-input multiple-output (MIMO) communications. However, the interference structure between transmission directions does not necessarily correlate. The obtained quality of service at the receiver may differ significantly from the desired one if the transmission parameters are assigned based on the reverse link measurements only. In this paper, the performance of an orthogonal frequency division multiplexing (OFDM) cellular system with adaptive MIMO transmission is studied in the presence of non-reciprocal inter-cell interference when the downlink interference structure is known at the receiver and only limited feedback information about the interference is available at the transmitter. The results are compared to those with perfectly known interference structure per each sub-carrier. The system level impact of realistic interference non-reciprocity scenarios is studied via network simulations. Linear minimum mean squared error (MMSE) filter is applied at the receiver to suppress the impact of structured inter-cell interference together with a simple and bandwidth efficient closed-loop compensation algorithm. Both link and system level simulation results show that the proposed compensation algorithm with a simple scalar power offset feedback combined with interference suppression at the receiver results in nearly the same performance as the ideal case     

Stability of Cahn‐Hilliard fronts

We prove stability of the kink solution of the Cahn‐Hilliard equation ∂_tu = ∂( ∂u − u/2 + u³/2), x ∈ ℝ. The proof is based on an inductive renormalization group method, and we obtain detailed asymptotics of the solution as t → ∞. We prove stability of the kink solution of the Cahn‐Hilliard equation ∂_tu = ∂( ∂u − u/2 + u³/2), x ∈ ℝ. The proof is based on an inductive renormalization group method, and we obtain detailed asymptotics of the solution as t → ∞. © 1999 John Wiley & Sons, Inc.     

Energy-Aware Interoperability of Manet and 4g Ran Routing

The requirements for telecommunication at 2012 are estimated to be on such demanding level that the 3G technologies will not be sufficient. It is unlikely that the 3G Radio Access Network (RAN) would scale up i.e., Fourth Generation (4G) RAN will need to be developed. The requirements for 4G are demanding and the level of uncertainty is high. The novel ad hoc networking technologies could provide flexible solutions for the 4G RAN and extend the operator radio coverage. Combining these differing communication technologies provides insight for the 4G RAN design. This paper analyses the Mobile Ad hoc Networks (MANET) requirements against the 4G requirements in terms of energy conservation. We find that there is mismatch between these two sets of requirements. Nevertheless, we demonstrate how these two approaches could co-exist in a mutually beneficial way. Finally, we propose interoperability requirements for MANET and 4G routing from the perspective of energy conservation. Harri Paloheimo is a researcher in Networking Technologies Laboratory at Nokia Research Center, Helsinki. In addition, he is a post graduate student in Telecommunications Software and Multimedia Laboratory, Department of Computer Science and Engineering, Helsinki University of Technology. He received M.Sc. degree majoring in space technology from Department of Electrical and Communications Engineering, Helsinki University of Technology in 2000. He currently works on next generation wireless networks with special interest in hybrid and relay networking solutions. Sudhir Dixit is currently a Nokia Research Fellow and works on next generation wireless networks. From 1996 to 2003 he was a Senior Research Manager, focusing on IP/ATM, wireless, content networks, and optical networks. Prior to that he worked at NYNEX Science & Technology (now Verizon), GTE (now Verizon), Codex Motorola, Wang, Harris, and STL (now Nortel Europe Labs). He has published or presented over 150 papers, published three books, and holds 14 patents. He is on the Editorial Board of the IEEE Communications Magazine, Springer's Wireless Personal Communications Journal, and KIC's Journal of Communications and Networks. He received a B.E. degree from MANIT, Bhopal, India, an M.E. degree from BITS, Pilani, India, a Ph.D. degree from the University of Strathclyde, Glasgow, Scotland, and an M.B.A. degree from Florida Institute of Technology, Melbourne. He is a Fellow of IEE (UK) and IETE (India). He represents Nokia on the Steering Board of the Wireless World Research Forum, and is also Vice Chair of the SIG on Self-Organization of Wireless World Systems. Dr.Tech. Antti Ylä-Jääski is a Professor of Telecommunications Software, Telecommunications Software and Multimedia Laboratory, Department of Computer Science and Engineering, Helsinki University of Technology. He is also a Research Fellow in Network Technologies Laboratory, Nokia Research Center, Helsinki. Prof Dr.Tech. Antti Ylä-Jääski received his PhD in ETH Zuerich 1993. Antti has worked with Nokia 1994–2004 in several research management positions with focus on future Internet technologies, mobile networks, applications, services, service management and service architectures. He has published about 30 articles and he holds several approved patents. Antti's current research interests include mobile networking, heterogeneous network environments, services, service architectures, service management and security issues.     

Parallelized Bayesian inversion for three-dimensional dental X-ray imaging

Diagnostic and operational tasks based on dental radiology often require three-dimensional (3-D) information that is not available in a single X-ray projection image. Comprehensive 3-D information about tissues can be obtained by computerized tomography (CT) imaging. However, in dental imaging a conventional CT scan may not be available or practical because of high radiation dose, low-resolution or the cost of the CT scanner equipment. In this paper, we consider a novel type of 3-D imaging modality for dental radiology. We consider situations in which projection images of the teeth are taken from a few sparsely distributed projection directions using the dentist's regular (digital) X-ray equipment and the 3-D X-ray attenuation function is reconstructed. A complication in these experiments is that the reconstruction of the 3-D structure based on a few projection images becomes an ill-posed inverse problem. Bayesian inversion is a well suited framework for reconstruction from such incomplete data. In Bayesian inversion, the ill-posed reconstruction problem is formulated in a well-posed probabilistic form in which a priori information is used to compensate for the incomplete information of the projection data. In this paper we propose a Bayesian method for 3-D reconstruction in dental radiology. The method is partially based on Kolehmainen et al. 2003. The prior model for dental structures consist of a weighted /spl lscr//sup 1/ and total variation (TV)-prior together with the positivity prior. The inverse problem is stated as finding the maximum a posteriori (MAP) estimate. To make the 3-D reconstruction computationally feasible, a parallelized version of an optimization algorithm is implemented for a Beowulf cluster computer. The method is tested with projection data from dental specimens and patient data. Tomosynthetic reconstructions are given as reference for the proposed method.     

An Integrated Digital CMOS Time-to-Digital Converter with Sub-Gate-Delay Resolution

An integrated digital CMOS time-to-digital converter with sub-gate delay LSB width and 50 ps single-shot precision -value has been designed and implemented for a laser range-finding application. The measurement is based on a counter and a novel two-step parallel interpolation that uses only 32 delay elements to provide 128 LSBs in the interpolator within the reference clock cycle. The circuit was fabricated in the AMS 0.8 m CMOS process and the current consumption of the circuit is <20 mA from a single +5 V supply.     

Link and System Level Performance of Multiuser Detection CDMA Uplink

The link level performance and the cellular systemcapacity in the uplink direction of a CDMA cellularsystem utilising multiuser detection base stationreceivers is analysed by simulation. In the receiver,parallel multistage multiuser detection is employedtogether with two-antenna diversity reception and fastclosed-loop power control. A system level simulator isbuilt to utilise the link level simulation results andto show the increase in cellular capacity obtained byusing multiuser detection. The capacity is studied inurban micro and macro-cell environments utilising thechannel models developed in the European CODITproject. The modelling of the environment specific andCDMA specific features is considered in the systemsimulator. The system level simulator is calibratedwith analytical capacity calculations.     

Transformation process of laser ablated PZT thin films

Transformation behavior of piezoelectric lead zirconate titanate (PZT) thin films prepared by laser ablation on unheated Al₂O₃ substrates was investigated within a broad temperature region. As-deposited films were mainly amorphous containing some microcrystalline perovskite and pyrochlore phases. The rhombohedral perovskite was the main phase in the films annealed between 500 and 800°C. These films also contained some pyrochIore, PbTiO₃, PbO, and ZrO₂. The PbO and ZrO₂ disappeared in the optimal annealing temperature interval of 700 to 800°C. Decomposition reactions took place above 800°C due to evaporation of lead and diffusion reactions occurred between substrate and film so that the films annealed at 1100°C consisted of ZrO₂, TiO₂, and PbO.     

Binary Lead Fluoride Pb3F8

The binary lead fluoride Pb₃F₈ was synthesized by the reaction of anhydrous HF with Pb₃O₄ or by the reaction of BrF₃ with PbF₂. The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS ¹⁹F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound.     

Determination of 14C, 55Fe, 63Ni and gamma emitters in activated RPV steel samples: a comparison between calculations and experimental analysis

Journal of Radioanalytical and Nuclear Chemistry - Determination of 14C, 55Fe, 63Ni and gamma emitters in two different types of activated reactor pressure vessel (RPV) steel samples were carried...