In this paper the effect of antenna integration in typical UWB consumer electronic products on the entire system performance is evaluated for a system model based on MB-OFDM. The antenna in its specific integration sc...
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In this paper the effect of antenna integration in typical UWB consumer electronic products on the entire system performance is evaluated for a system model based on MB-OFDM. The antenna in its specific integration scenario is characterized by the full wave FDTD method. Different deterministic indoor channels are characterized using ray-tracing simulation. Based on the analysis the channel transfer function, including the antennas can be derived in terms of S-parameters. From the transfer function of the antennas and the channels different antenna and channel related measures like RMS delay spread or frequency depended radiation pattern are derived. In order to evaluate the impact on the entire link performance a MatLab Simulink model of a UWB system is used to model the entire system. The system related parameters like BER (Bit Error Rate) are evaluated with reference to different antenna integrations and link scenarios.
Acoustic vector sensors that measure pressure and orthogonal particle velocity are gaining widespread interest. Predicting their performance requires calculating the pressure field and the velocity fields, which requi...
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ISBN:
(纸本)9781467399791
Acoustic vector sensors that measure pressure and orthogonal particle velocity are gaining widespread interest. Predicting their performance requires calculating the pressure field and the velocity fields, which require spatial gradients of the pressure field. In typical hydrophone applications, significant computational savings are realized by using reciprocity to generate the pressure field as a function of source position rather than receive position. However, the presence of the spatial gradients in the velocity fields means that reciprocity cannot be used to model the vector field for inverse problems. Instead, the inverse vector velocity field must be computed point by point, even for the simplest environments. Examples of this effect are demonstrated by the derivation of analytic expressions for pressure and particle velocity in a Pekeris waveguide. These simple waveguide results are extended to arbitrary, range-dependent, environment parameters using a parabolic equation model.
On 3 June 2004, a bolide was observed over British Columbia, Washington, Oregon, and Idaho. In addition to eyewitness accounts, the event was recorded on videotape and at similar to 100 seismometers located in Washing...
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On 3 June 2004, a bolide was observed over British Columbia, Washington, Oregon, and Idaho. In addition to eyewitness accounts, the event was recorded on videotape and at similar to 100 seismometers located in Washington State and southern British Columbia. Seismic records are consistent with a terminal burst rather than the hypersonic shock of the meteors passage through the atmosphere. Arrival times from seismic waveform data are used to obtain an accurate source location for this terminal burst. The source location can effectively be considered to be ground-truth for assessing current atmospheric models and infrasound propagation algorithms. We observe clear infrasonic signals associated with the terminal burst of the fireball at infrasound stations I56US and I57US in Washington State and California, respectively. At I56US we observe at least four distinct acoustic arrivals, for which we are able to model three using a state-of-the-art atmospheric model ( the Ground-to-Space (G2S) model) and both ray-tracing and parabolic equation propagation algorithms. To our knowledge, this is the first study in which a complex sequence of arrival packets at an individual station has been successfully modeled by range-dependent ducting and specular reflection off terrain gradients. At I57US a single coherent acoustic signal was observed, which we are unable to satisfactorily model. This could be due to errors in the specification of the background atmosphere, incorrect assumptions and approximations inherent to the acoustic propagation algorithms, and the greater range of propagation, which amplifies the effect of errors in source location and the atmospheric specifications.
Mobile operators need to deploy dense LTE-Advanced small-cell networks in the next few years to cope with the growing mobile data traffic demand. Prediction models and mobile network design tools need to radically evo...
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ISBN:
(纸本)9781479944484
Mobile operators need to deploy dense LTE-Advanced small-cell networks in the next few years to cope with the growing mobile data traffic demand. Prediction models and mobile network design tools need to radically evolve to allow a proper evaluation, and then design and optimization of cost-efficient heterogeneous networks. This paper introduces a comprehensive solution for cost and performance analysis. A ray-based propagation model and a 3D traffic mapping tool are used to feed a 3D LTE-A simulator. Then, a case study of a North American city addresses the impact of modeling tools on outdoor small-cell deployment costs. The analysis highlights some applicative results: The identification of hotspots within macro-cells enabled by the presented tool shows a significant impact on deployment costs (18% less than with only per-sector information). A 2D modeling approach overestimates macro offload, leading to an under-designed small-cell network that could be prevented thanks to 3D tools. This qualitative comparison is useful to understand the significance of modeling tools for cost and performance analysis of future heterogeneous networks.
In this paper, the evolution of ITU-R rain attenuation prediction methods from previous versions to the most recent one is evaluated in terms of their performance in predicting attenuation, as compared to experimental...
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ISBN:
(纸本)9781467394932
In this paper, the evolution of ITU-R rain attenuation prediction methods from previous versions to the most recent one is evaluated in terms of their performance in predicting attenuation, as compared to experimental data collected from 77 terrestrial links located in 16 countries. Test results indicate that the current version performs better than the previous one. However, a prediction method that introduces the concept of effective rain rate and uses the full rainfall rate distribution for the prediction of the rain attenuation distribution is also included in the comparison and outperforms current ITU-R model.
When conditions are right, temperature gradients and fast jets of wind can help to establish atmospheric ducts—pathways in the atmosphere that promote the propagation of low-frequency acoustic waves (infrasound)—acr...
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When conditions are right, temperature gradients and fast jets of wind can help to establish atmospheric ducts—pathways in the atmosphere that promote the propagation of low-frequency acoustic waves (infrasound)—across long distances. Atmospheric ducts are part of the basis behind over-the-horizon radar, the source of some particularly clear mirages, and a channel through which sounds can travel relatively unperturbed across vast distances.
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