December 2002, Volume 11, Number 4
Wireless Cellular Mobile Communications
In this article is briefly reviewed the history of wireless cellular mobile communications, examined the progress in current second generation (2G) cellular standards and discussed their migration to the third generation (3G). The European 2G cellular standard GSM and its evolution phases GPRS and EDGE are described somewhat in detail. The third generation standard UMTS taking up on GSM/GPRS core network and equipped with a new advanced access network on the basis of code division multiple access (CDMA) is investigated too. A sketch of the perspective of mobile communication beyond 3G concludes this article.
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MIMO Spatial Diversity Communications - Signal Processing and Channel Capacity
This paper derives an equivalent discrete channel model for MIMO spatial diversity communications generally considering multidimensional spatial branch symbols and arbitrary path delays. This model is subsequently used for the information capacity evaluation under various special cases.
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L. Burget, P. Motlicek, F. Grezl, P. Jain
Distributed Speech Recognition
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.
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L. Dobos, J. Goril
Call Admission Control in Mobile Wireless
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.
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J. Novikmec, L. Dobos
Mobile Access to the Internet
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.
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Wireless Local Area Networks: A Comprehensive Guide
Nowadays the demand on exchange of information is higher and higher. During recent years rapid development of radio communication, both mobile and non-mobile has been experienced. Because of need of wider frequency range and expansive number of services using "the air" as the medium, higher frequencies have to be applied. This paper deals mainly with wireless LAN using license-free band such as 2.4GHz (ISM) or 5.2GHz.
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V. Wieser, K. Hrudkay
Mutual Interference Models for CDMA Mobile Communication Networks
Nowadays we are witnesses of a huge development one of the most progressive communication technology - mobile networks. The main problem in these networks is an elimination of the mutual interference, which, mainly in non-orthogonal CDMA networks, is the principal obstacle for reaching high transmission rates The aim of this contribution is to give simplified view to mutual interference models for orthogonal and non-orthogonal CDMA networks. The contribution is intended mainly for PhD. students to help them to obtain an orientation in such a complicated areas, as the interference models for CDMA networks are.
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K. Hrudkay, V. Wieser
Power Control Imperfection in CDMA Systems with Adaptive Antennas
This paper deals with a simulation of cellular CDMA system using base station adaptive antennas. The model assumes two tiers area, four types of antennas, lognormal shadowing corresponding to three types of environments and perfect power control or two values of power control error, respectively. The capacity of system in up-link is evaluated by a number of mobile stations with higher signal to interference ratio than threshold with given outage probability.
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P. Ledl, P. Pechac
Area Coverage Simulations for Millimeter Point-to-Multipoint Systems Using Building Blockage
Area 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.
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M. Valek, S. Zvanovec, P. Pechac
Indoor Propagation Measurement for WLAN Systems Operating in 2.45 GHz ISM Band
For 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.
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