2005/1

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    Generator of Time Series of Rain Attenuation: Results of Parameter Extraction
    (Společnost pro radioelektronické inženýrství, 2005-04) Grabner, Martin; Fiebig, Uwe-Carsten; Kvicera, Vaclav
    Rain attenuation has a significant impact on the availability of millimeter wave communication systems. In order to dynamically simulate such radio systems, several generators of artificial time series of rain attenuation have been developed. This paper briefly describes the DLR channel model and presents the results of model parameter extraction from time series measured on terrestrial microwave paths in the Czech Republic.
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    Impact of Ultra Wide Band (UWB) on Macrocell Downlink of DCS-1800 and GSM-900 Systems
    (Společnost pro radioelektronické inženýrství, 2005-04) Taha-Ahmed, Bazil; Calvo-Ramon, Miguel; de Haro-Ariet, Leandro
    The effect of UWB interference on the DCS-1800 and GSM-900 downlink is studied for different UWB power density. For high UWB power density (-70 dBm/MHz), the effect of UWB signals is very high when the distance between UWB transmitter and DCS-1800 receiver is less than 1 m. For low UWB power density (-100 dBm/MHz), the effect of the UWB signals is quasi null even if the distance between the UWB transmitter and the DCS-1800 receiver is 0.5 m. It is found that the spectrum mask proposed by the FCC for indoor application (-53 dBm/MHz in the DCS-1800 band and -41 dBm/MHz in the GSM-900 band) is very high to be tolerated by the two mobile systems and we have to propose another spectrum mask with lower UWB power density.
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    An Efficient and Effective Pilot Space-Time Adaptive Algorithm for Mobile Communication Systems
    (Společnost pro radioelektronické inženýrství, 2005-04) Landqvist, Ronnie; Mohammed, Abbas
    In this paper we present a new adaptive space-time algorithm for mitigating the effects of CCI and ISI and minimizing the probability of error in mobile communication systems, and evaluate its performance for different mobile velocities. The proposed algorithm is computationally efficient and provides better performance than the conventional RLS algorithm.
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    Intelligent FDSS Overlay on GSM System (Uplink Analysis)
    (Společnost pro radioelektronické inženýrství, 2005-04) Taha-Ahmed, Bazil; Calvo-Ramon, Miguel; de Haro-Ariet, Leandro
    The overlay of an intelligent frequency diversity spread spectrum system (FDSS) on the (GSM) system is studied. The uplink capacity of both systems is given using a model of 36 hexagonal macrocells. Performance of GSM and FDSS users is investigated. An original GSM system with 48 users/macrocell can be substituted by a mixed system, which has GSM system capacity of 48 users/macrocell and FDSS system capacity of 128 users/macrocell.
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    Methods for Speech SNR Estimation: Evaluation Tool and Analysis of VAD Dependency
    (Společnost pro radioelektronické inženýrství, 2005-04) Vondrasek, Martin; Pollak, Petr
    The dynamic range of broadband digital system is mostly limited by harmonics and spurious arising from ADC nonlinearity. The nonlinearity may be described in several ways. The distinction between static and dynamic contributions has strong theoretical motivations but it is difficult to independently measure these contributions. A more practical approach is based upon analysis of the complex spectrum, which is well defined, easily measured, and may be used to optimize the ADC working point and to somehow characterize both static and dynamic nonlinearity. To minimize harmonics and spurious components we need a sufficient level of input noise (dither), which destroys the periodicity at multistage pipelined ADC, combined with a careful analysis of the different sources of nonlinearity.