Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Channel Acquisition for Massive MIMO-OFDM with Adjustable Phase Shift Pilots  [PDF]
Li You,Xiqi Gao,A. Lee Swindlehurst,Wen Zhong
Mathematics , 2015,
Abstract: We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made non-overlapping with proper phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.
Focus Shift and Outsourcing in University Libraries’Acquisition and Cataloguing
Chunlan Qiu,Yonglin Xiao,Rongshuang Lu
International Journal of Business and Management , 2009, DOI: 10.5539/ijbm.v3n3p129
Abstract: Focus shift and outsourcing in university libraries’ acquisition and cataloguing, which are the trends of re-composition and optimized allocation of social resources in market mechanism, will help to improve the quality of document construction as well as the efficiency of acquisition and cataloguing and allocate human resources in a more reasonable way. Nowadays, outsourcing of books has become usual practice in libraries. It should be the future focus to construct scientific and reasonable collection structure, acquire books in different channels, forms and at different levels and to extend acquisition and cataloguing services.
From Antenna to Antenna: Lateral Shift of Olfactory Memory Recall by Honeybees  [PDF]
Lesley J. Rogers, Giorgio Vallortigara
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002340
Abstract: Honeybees, Apis mellifera, readily learn to associate odours with sugar rewards and we show here that recall of the olfactory memory, as demonstrated by the bee extending its proboscis when presented with the trained odour, involves first the right and then the left antenna. At 1–2 hour after training using both antennae, recall is possible mainly when the bee uses its right antenna but by 6 hours after training a lateral shift has occurred and the memory can now be recalled mainly when the left antenna is in use. Long-term memory one day after training is also accessed mainly via the left antenna. This time-dependent shift from right to left antenna is also seen as side biases in responding to odour presented to the bee's left or right side. Hence, not only are the cellular events of memory formation similar in bees and vertebrate species but also the lateralized networks involved may be similar. These findings therefore seem to call for remarkable parallel evolution and suggest that the proper functioning of memory formation in a bilateral animal, either vertebrate or invertebrate, requires lateralization of processing.
An FFT-Based Approach in Acceleration of Discrete Green's Function Method for Antenna Analysis
Salma Mirhadi;Mohammad Soleimani;Ali Abdolali
PIER M , 2013, DOI: 10.2528/PIERM12121407
Abstract: In this paper, the fast Fourier transform (FFT) to perform spatial convolutions of the time domain discrete Green's functions (DGF) method related to the analysis of the antenna with more than one dimension has been proposed. For this aim, the discrete Green's functions and the currents on the antenna have been appropriately defined periodic so as to use the zero padded fast Fourier transform. The computational complexity of this approach is ( log()), contrary to ()for direct implementation of the convolutions. Simulation results demonstrate the great efficiency of the FFTbased spatial convolutions in the modeling of planar antennas.
Secure and Green SWIPT in Distributed Antenna Networks with Limited Backhaul Capacity  [PDF]
Derrick Wing Kwan Ng,Robert Schober
Mathematics , 2014,
Abstract: This paper studies the resource allocation algorithm design for secure information and renewable green energy transfer to mobile receivers in distributed antenna communication systems. In particular, distributed remote radio heads (RRHs/antennas) are connected to a central processor (CP) via capacity-limited backhaul links to facilitate joint transmission. The RRHs and the CP are equipped with renewable energy harvesters and share their energies via a lossy micropower grid for improving the efficiency in conveying information and green energy to mobile receivers via radio frequency (RF) signals. The considered resource allocation algorithm design is formulated as a mixed non-convex and combinatorial optimization problem taking into account the limited backhaul capacity and the quality of service requirements for simultaneous wireless information and power transfer (SWIPT). We aim at minimizing the total network transmit power when only imperfect channel state information of the wireless energy harvesting receivers, which have to be powered by the wireless network, is available at the CP. In light of the intractability of the problem, we reformulate it as an optimization problem with binary selection, which facilitates the design of an iterative resource allocation algorithm to solve the problem optimally using the generalized Bender's decomposition (GBD). Furthermore, a suboptimal algorithm is proposed to strike a balance between computational complexity and system performance. Simulation results illustrate that the proposed GBD based algorithm obtains the global optimal solution and the suboptimal algorithm achieves a close-to-optimal performance. Besides, the distributed antenna network for SWIPT with renewable energy sharing is shown to require a lower transmit power compared to a traditional system with multiple co-located antennas.
Comparison of Different Methods for the Experimental Antenna Phase Center Determination Using a Planar Acquisition System
Pablo Padilla de la Torre;Jose-Manuel Fernandez Gonzalez;Jose Luis Padilla;Gonzalo Exposito-Dominguez;Manuel Sierra-Castaner;Belen Galocha Iraguen
PIER , 2013, DOI: 10.2528/PIER12112108
Abstract: This work provides the comparison of different methods for the experimental determination of the phase center location of an antenna. The phase center position is determined by means of measured data obtained with a planar scanning system and computed with different methods: a least squares fit method with and without weighting coefficients and a directivity-based plane wave spectrum (PWS) analysis method. A study of the phase center position for different microwave antennas is provided. The results of the different methods are presented and compared, along with the confidence interval of the phase center values due to the uncertainties of the acquisition system.
Analysis of Radiation Characteristics of a Probe-Excited Rectangular Ring Antenna by the Dyadic Green's Function Approach
Suthasinee Lamultree;Chuwong Phongcharoenpanich;Sompol Kosulvit;Monai Krairiksh
PIER B , 2009, DOI: 10.2528/PIERB08101602
Abstract: Abstract-Radiation characteristics of a probe-excited rectangular ring antenna are investigated by using the dyadic Green function approach. The radiation characteristics, such as radiation pattern, beam-peak direction, half-power beamwidth and directivity, are analyzed. For the specified operating frequency, the ring width and ring height are selected as the same crosssectional dimension of rectangular waveguide operated at the dominant mode. The effects of the excited probe and rectangular ring to the modal distributions are described. For the desired modal distribution, the directivity primarily depends on the ring lengths. For compact size of the proposed antenna, the ring length of 0.4λ is chosen to provide a bidirectional pattern with the calculated half-power beamwidth in -plane and -plane of 100 and 69 degrees respectively, and directivity of 4.43 dBi. Furthermore, the prototype antenna was fabricated and measured. The coincided results between the theory and the experiment are obtained.
Design and Fabrication of Wideband Archimedean Spiral Antenna Based Ultra-Low Cost ``Green'' Modules for RFID Sensing and Wireless Applications
Yasar Amin;Qiang Chen;Li-Rong Zheng;Hannu Tenhunen
PIER , 2012, DOI: 10.2528/PIER12070807
Abstract: A parametric analysis is performed for a wideband Archimedean spiral antenna in recognition of an emerging concept to integrate RFID along with several applications by using a single antenna. The antenna is fabricated using state-of-the-art inkjet printing technology on various commercially available paper substrates to provide the low-cost, flexible RF modules for the next generation of "green" electronics. The effects on electromagnetic characteristics of the planar Archimedean spiral antenna, due to the use of paper are investigated besides other parameters. The proposed antenna is evaluated and optimized for operational range from 0.8-3.0 GHz. It exhibits exceptional coverage throughout numerous RFID ISM bands so do for other wireless applications.
Chemoresistance acquisition induces a global shift of expression of aniogenesis-associated genes and increased pro-angogenic activity in neuroblastoma cells
Martin Michaelis, Denise Klassert, Susanne Barth, Tatyana Suhan, Rainer Breitling, Bernd Mayer, Nora Hinsch, Hans W Doerr, Jaroslav Cinatl, Jindrich Cinatl
Molecular Cancer , 2009, DOI: 10.1186/1476-4598-8-80
Abstract: Bioinformatics analysis of gene expression data revealed that expression of angiogenesis-associated genes significantly differs between chemosensitive and chemoresistant neuroblastoma cells. A subsequent systematic analysis of a panel of 14 chemosensitive and chemoresistant neuroblastoma cell lines in vitro and in animal experiments indicated a consistent shift to a more pro-angiogenic phenotype in chemoresistant neuroblastoma cells. The molecular mechanims underlying increased pro-angiogenic activity of neuroblastoma cells are individual and differ between the investigated chemoresistant cell lines. Treatment of animals carrying doxorubicin-resistant neuroblastoma xenografts with doxorubicin, a cytotoxic drug known to exert anti-angiogenic activity, resulted in decreased tumour vessel formation and growth indicating chemoresistance-associated enhanced pro-angiogenic activity to be relevant for tumour progression and to represent a potential therapeutic target.A bioinformatics approach allowed to identify a relevant chemoresistance-associated shift in neuroblastoma cell biology. The chemoresistance-associated enhanced pro-angiogenic activity observed in neuroblastoma cells is relevant for tumour progression and represents a potential therapeutic target.Neuroblastoma is the most frequent extracranial solid tumour of childhood. About half of all neuroblastoma patients are diagnosed with high-risk disease with overall survival rates below 40% despite intensive multimodal treatment [1]. Therapy failure is basically caused by acquired chemoresistance. Primary tumours usually respond to initial chemotherapy. However, a significant fraction of tumours reappear as chemoresistant recidives [2].Acquisition of chemoresistance under therapy may affect the biology of neuroblastoma and other tumour cells [3-9]. Mostly a shift towards a more malignant phenotype is observed indicating cancer progression [3,4,6-9]. Molecular changes in different signalling pathways including apoptos
Acquisition system for the CLIC Module  [PDF]
Sebastien Vilalte
Physics , 2011,
Abstract: The status of R&D activities for CLIC module acquisition are discussed [1]. LAPP is involved in the design of the local CLIC module acquisition crate, described in the document Study of the CLIC Module Front-End Acquisition and Evaluation Electronics [2]. This acquisition system is a project based on a local crate, assigned to the CLIC module, including several mother boards. These motherboards are foreseen to hold mezzanines dedicated to the different subsystems. This system has to work in radiation environment. LAPP is involved in the development of Drive Beam stripline position monitors read-out, described in the document Drive Beam Stripline BPM Electronics and Acquisition [3]. LAPP also develops a generic acquisition mezzanine that allows to perform all-around acquisition and components tests for drive beam stripline BPM read-out.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.