			Home About us Contact

Coverage Area (coverage + area)

Distribution by Scientific Domains

Engineering	83%

Selected Abstracts

Precision enhancement in ETSI-Hata propagation model tuning using experimental data in a dense urban area

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2010
Mehran Atamanesh
Abstract In this paper an enhanced ETSI-Hata propagation model tuning is presented. The three-dimensional (3D) digital terrain map (DTM) was included in the simulation process. For the enhancement of the model tuning process and precision verification of ETSI-Hata model, the real 3D map of the buildings of the simulated area was incorporated over the DTM. Multiple knife edge diffraction method and the antenna effective height method were used to calculate the diffraction loss. This method was applied for a real urban scenario. For every sector in the coverage area, a tuned model was exploited. Using a genetic algorithm, frequency planning for the entire urban area was performed, which resulted in an improvement in the quality of service. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Providing multimedia communications services from high altitude platforms

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2001
D. Grace
Abstract System level design considerations for high altitude platforms operating in the mm-wave bands are examined. Propagation effects in these bands are outlined, followed by a brief introduction to different platform scenarios. Ground-based and platform-based fixed wireless access scenarios are considered, and it is shown that using a platform, a single base station can supply a much larger coverage area than a terrestrial base station. The effects on performance of platform displacement from its desired location with both fixed and steerable antennas are also examined. It is shown that steerable antennas are of most use when fixed stations are immediately below the platform, with no benefit for fixed stations on the edge of coverage. The bandwidths required to serve several traffic distributions (suburbs and city centre based) are evaluated using the Shannon equation. It is shown that capacity can be constrained when users are located in the city centres, despite longer line of sight paths to users out in the suburbs. The effects of temporal changes in the spatial traffic distribution are investigated. It is shown that bandwith requirements can be reduced if the platform moves to track these changes. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Application of GIS for processing and establishing the correlation between weather radar reflectivity and precipitation data

METEOROLOGICAL APPLICATIONS, Issue 1 2005
Y. Gorokhovich
Correlation between weather radar reflectivity and precipitation data collected by rain gauges allows empirical formulae to be obtained that can be used to create continuous rainfall surfaces from discrete data. Such surfaces are useful in distributed hydrologic modelling and early warning systems in flood management. Because of the spatial relationship between rain gauge locations and radar coverage area, GIS provides the basis for data analysis and manipulation. A database of 82 radar stations and more than 1500 rain gauges in continental USA was compiled and used for the continuous downloading of radar images and rain data. Image sequences corresponding to rain events were extracted for two randomly selected radar stations in South and North Carolina. Rainfall data from multiple gauges within the radar zone of 124 nautical miles (nm) (,230 km) were extracted and combined with corresponding reflectivity values for each time interval of the selected rain event. Data were normalised to one-hour intervals and then statistical analysis was applied to study the potential correlation. Results of regression analysis showed a significant correlation between rain gauge data and radar reflectivity values and allowed derivation of empirical formulae. Copyright © 2005 Royal Meteorological Society. [source]

Wide coverage area of UHF-band RFID system using a pattern reconfigurable antenna

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007
Hanphil Rhyu
Abstract A new type of a reader antenna for a UHF-band RFID system is proposed to cover a wider area. The proposed antenna consists of a circular polarized patch element, an omnidirectional electrical loop element, and a feeding network. By combining two antenna elements whose radiation patterns and half-power beamwidths (HPBW) are different from each other, the coverage area of the RFID system is increased. The experimental results show the proposed antenna has a HPBW of more than 120° and works well in the UHF band RFID system. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2154,2157, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22694 [source]

Performance evaluation of adaptive routing algorithms in packet-switched intersatellite link networks

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2002
Mihael Mohor
Abstract This paper addresses the performance evaluation of adaptive routing algorithms in non-geostationary packet-switched satellite communication systems. The dynamic topology of satellite networks and variable traffic load in satellite coverage areas, due to the motion of satellites in their orbit planes, pose stringent requirements to routing algorithms. We have limited the scope of our interest to routing in the intersatellite link (ISL) segment. In order to analyse the applicability of different routing algorithms used in terrestrial networks, and to evaluate the performance of new algorithms designed for satellite networks, we have built a simulation model of a satellite communication system with intersatellite links. In the paper, we present simulation results considering a network-uniform source/destination distribution model and a uniform source,destination traffic flow, thus showing the inherent routing characteristics of a selected Celestri-like LEO satellite constellation. The updates of the routing tables are centrally calculated according to the Dijkstra shortest path algorithm. Copyright © 2002 John Wiley & Sons, Ltd. [source]