2002/4
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Recent Submissions
- ItemArea Coverage Simulations for Millimeter Point-to-Multipoint Systems Using Building Blockage(Společnost pro radioelektronické inženýrství, 2002-12) Ledl, P.; Pechač, PavelArea coverage simulation results for LMDS or PMP systems in millimeter waveband are presented in this paper. Area coverage simulations were performed according to ITU-R P.1410 model, where Rayleigh statistical distribution with g = 7.95 is used to model the building heights. Morphological data of the city of Prague were used to calculate a new set of values g. The model was optimized to local conditions. Area coverage prediction results using the new set of values g are also presented. Accuracy of the model was increased due to suggested modification.
- ItemCall Admission Control in Mobile Wireless(Společnost pro radioelektronické inženýrství, 2002-12) Dobos, L.; Goril, J.Some problems related to wireless network access are discussed in the article. Special attention is paid to Medium Access Control and Call Admission Control. Both have direct impact on communication link accession. While the first one dictates how to, the second one decides who can access the link. The problems with wireless medium access are mentioned and requirements on MAC protocols are named. Also need for CAC algorithms is illustrated and simple functional example is proposed. Finally, the reasons for future enhancements are shortly discovered.
- ItemMobile Access to the Internet(Společnost pro radioelektronické inženýrství, 2002-12) Novikmec, J.; Dobos, L.In this paper various aspects of mobile access to Internet are discussed. We mention general Internet protocols and mobile enhancements and also future models that will be used in near future.
- ItemDistributed Speech Recognition(Společnost pro radioelektronické inženýrství, 2002-12) Burget, L.; Motlicek, P.; Grezl, F.; Jain, P.This article discusses possibilities of integrating speech technology into wireless technology, allowing voice input for wireless devices. Distributed speech recognition concept and activities related to its standardization are presented. First ETSI DSR MFCC based standard is described. Work on its extension to improve robustness resulting in new standard is also presented.
- ItemIndoor Propagation Measurement for WLAN Systems Operating in 2.45 GHz ISM Band(Společnost pro radioelektronické inženýrství, 2002-12) Valek, M.; Zvanovec, S.; Pechač, PavelFor a planning of indoor Wireless LAN systems working in the ISM band, the signal propagation prediction is needed. In this article, the measurement campaign based on two types of measurements at 2.45 GHz is introduced. The first type of the measurement was a classical narrowband signal level measurement within indoor scenario without presence of people. The aim of this measurement was to find empirical parameters for COST231 Multi-Wall and One-Slope models. In order to statistically describe the time varying nature of the received envelope of the signal, at WLAN 2.45 GHz band, the second part of measurement campaign was accomplished. In this case, the signal level was measured using commercial WLAN PCMCIA cards in two notebooks. Probability density functions and corresponding cumulative distribution functions were set and discussed based on the specific locations and orientation of one of the notebooks. Results from both measurement campaigns were compared and conclusions are drawn for the needs of practical planning of indoor WLAN systems coverage.