Search results for "BAND"
showing 10 items of 2610 documents
Conduction band polarization in some CMR materials
2000
First principles electronic structure calculations reveal certain important common features in the conduction band polarization of many of the newly examined colossal magnetoresistance (CMR) materials. Most CMR compounds seem to possess a localized, magnetic band slightly below the Fermi energy. This localized band transfers polarization to a relatively broad conduction band. The nature of the two bands in different systems can be quite distinct. In the perovskite-derived manganese oxides, the magnetic band is derived from $Mn t_{2g}$ states while the conduction band is derived from Mn e states. In the chalcospinel $Fe_{^0.^5}$ $Cu_{^0.^5}$ $Cr_{2}$$ S_{4}$ , the $Crt_{2g}$ states which are…
Multilevel Bandwidth and Radio Labelings of Graphs
2008
This paper introduces a generalization of the graph bandwidth parameter: for a graph G and an integer k ≤ diam(G), the k-level bandwidth Bk(G)of G is defined by Bk(G) = minγ max{|γ(x)-γ(y)|-d(x, y)+1 : x, y ∈ V (G), d(x, y) ≤ k}, the minimum being taken among all proper numberings γ of the vertices of G. We present general bounds on Bk(G) along with more specific results for k = 2 and the exact value for k = diam(G). We also exhibit relations between the k-level bandwidth and radio k-labelings of graphs from which we derive a upper bound for the radio number of an arbitrary graph.
Rigorous Multimode Equivalent Network Representation of Multilayer Planar Circuits
2018
The objective of this paper is to extend the use of the Multimode Equivalent Network formulation, originally developed to analyze waveguide junctions, to the analysis of planar circuits that include arbitrary rectangular printed, zero thickness metallizations together with internal and external ports in the transverse plane. The theoretical derivations lead to an accurate and computationally efficient tool for the analysis of boxed, multilayer microwave printed circuits. In addition to theory, the tool developed is used here to analyze two practical examples: a dual-bandpass and a 4-pole bandpass boxed microstrip filters. Good agreement with respect to commercial software tools and measurem…
Experiencing Broadband Society
2011
Julian Gebhardt, Greif Hajo, Raycheva Lilia, Claire Lobet-Maris & Lasen Amparo (eds), Experiencing Broadband Society (Frankfurt am Main and Oxford: Peter Lang, 2010), 206 pp., ISBN 978-3-631-58406-...
Doppler Shift Characterization of Wideband Mobile Radio Channels
2019
The prevailing approach for characterizing the Doppler shift (DS) of mobile radio channels assumes the transmission of an unmodulated carrier. This consideration is valid for the analysis of narrowband channels, but its pertinence is questionable in regards to the modeling of wideband channels. In this correspondence, we redefine the DS from a time-frequency analysis perspective that does not depend on the aforementioned assumption. We systematically demonstrate that the DS can be characterized by the instantaneous frequency of the channel transfer function. This generic definition makes evident a fundamental aspect of the DS that is seldom acknowledged, namely, the DS is a frequency-varyin…
Indoor localization using time difference of arrival with UWB signals and unsynchronized devices
2020
Abstract Indoor location using radio frequency (RF) signals has been traditionally focused mainly on RSSI and fingerprint techniques, because methods based on time of arrival (ToA) or time difference of arrival (TDoA) were not suitable for measuring short distances. However, the release of the IEEE 802.15.4a standard, the emergence of commercial ultra wide band (UWB) transceivers that are compliant to this norm and the integration of high frequency oscillators have permitted the design of more accurate indoor localization systems using the RF signal transmission time. In this paper, we propose an indoor localization system based on TDoA for UWB. The method implements an only one way transmi…
An Ergodic Sum-of-Cisoids Simulator for Multiple Uncorrelated Rayleigh Fading Channels Under Generalized Scattering Conditions
2012
In this paper, we present a new method for the design of ergodic sum-of-sinusoids (SOS) simulators for multiple uncorrelated narrowband Rayleigh fading channels. The method, which is intended for a special class of SOS models known as sum-of-cisoids (SOC) models, enables the generation of an unlimited number of mutually uncorrelated Rayleigh fading waveforms with specified autocorrelation properties. This is in contrast to all known methods proposed for SOS simulators, which are restricted to the simulation of multiple uncorrelated Rayleigh fading channels characterized by autocorrelation functions (ACFs) derived under the isotropic scattering assumption. The excellent performance of this n…
A Wideband MIMO Channel Model Derived From the Geometric Elliptical Scattering Model
2006
In this paper, we present a reference model for a wideband multiple-input multiple-output (MIMO) channel based on the geometric elliptical scattering model. The model takes into account the exact relationship between the angle of departure (AOD) and the angle of arrival (AOA). Based on this relationship, the statistical properties of the reference model are studied. Analytical solutions are presented for the three- dimensional (3D) space-time cross-correlation function (CCF), the temporal autocorrelation function (ACF), the 2D space CCF, and finally the frequency correlation function (FCF). The correlation properties are studied and visualized under the assumption of isotropic as well as no…
The generalized method of equal areas for the design of sum-of-cisoids simulators for mobile Rayleigh fading channels with arbitrary Doppler spectra
2011
We present in this paper a generalized version of the method of equal areas (MEA) that is well suited for the design of sum-of-cisoids (SOC) simulators for narrowband mobile Rayleigh fading channels characterized by any type of Doppler power spectral densities (DPSDs). Unlike the original MEA, the generalized MEA (GMEA) can be applied to the simulation of fading channels with asymmetrical DPSDs. This is an important feature because the simulation of such channels is of great interest for the laboratory analysis of mobile communication systems under non-isotropic scattering conditions. We show that irrespective of the underlying DPSD, the GMEA results in a very good approximation to the auto…
Architectures and protocols for mobile computing applications: a reconfigurable approach
2004
This work deals with reconfigurable control functions and protocols for supporting mobile computing applications in heterogeneous wireless systems like cellular networks and WLANs. The control functions are implemented in a software module, named Reconfigurable Access module for MObile computiNg applications (RAMON), placed in mobile and/or base stations. RAMON operates on abstract models of the main communication functions of a wireless systems (e.g., transmission over the radio channel, coding end error recovery, capacity sharing and packet scheduling, handover, congestion control, etc.). RAMON algorithms are programmed with reference to the abstract models, independently of specific radi…