2011/2

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Utilization of Selected Data Mining Methods for Communication Network Analysis
(Společnost pro radioelektronické inženýrství, 2011-06) Vranova, Zuzana; Ondryhal, Vojtech
The aim of the project was to analyze the behavior of military communication networks based on work with real data collected continuously since 2005. With regard to the nature and amount of the data, data mining methods were selected for the purpose of analyses and experiments. The quality of real data is often insufficient for an immediate analysis. The article presents the data cleaning operations which have been carried out with the aim to improve the input data sample to obtain reliable models. Gradually, by means of properly chosen SW, network models were developed to verify generally valid patterns of network behavior as a bulk service. Furthermore, unlike the commercially available communication networks simulators, the models designed allowed us to capture nonstandard models of network behavior under an increased load, verify the correct sizing of the network to the increased load, and thus test its reliability. Finally, based on previous experience, the models enabled us to predict emergency situations with a reasonable accuracy.
Compact and Sharp-Rejection Bandstop Filter Using Uniplanar Double Spiral Resonant Cells
(Společnost pro radioelektronické inženýrství, 2011-06) Lu, Ke; Wang, Guang-Ming; Xu, He-Xiu
A novel compact bandstop filter composed of three cascaded uniplanar double spiral resonant cells (UDSRCs) for high attenuation rates is presented. Through the equivalent circuit prediction and parametric analysis, it is found that the UDSRC exhibits two controllable transmission zeros with great design flexibility through tuning the geometry parameters in a small range. Then, the influence of the stage separation between each UDSRC is investigated in order to get the appropriate stage separation. After optimization, a demonstration bandstop filter has been fabricated and measured. The results show that the attenuation rates on the lower and upper sides are 95dB/GHz and 155dB/GHz, respectively. Without any shunt stubs introduced, the length and width of the three cells are 28% and 4% of the guided wavelength at the mid-stopband frequency.
An Issue of Boundary Value for Velocity and Training Overhead Using Cooperative MIMO Technique in Wireless Sensor Network
(Společnost pro radioelektronické inženýrství, 2011-06) Islam, Mohammad Rakibul
A boundary value of velocity of data gathering node (DGN) and a critical value for training overhead beyond which the cooperative communication in wireless sensor network will not be feasible is proposed in this paper. Multiple Input Multiple Outputs (MIMO) cooperative communication is taken as an application. The performance in terms of energy efficiency and delay for a combination of two transmitting and two receiving antennas is analyzed. The results show that a set of critical value of velocity and training overhead pair is present for the long haul communication from the sensors to the data gathering node. Later a graphical relation between boundary value of training overhead and velocity is simulated. A mathematical relation between velocity and training overhead is also developed. The effects of several parameters on training overhead and velocity are analyzed.
Effects of Imperfect Reference Signal Recovery on Performance of SC and SSC Receivers over Generalized Fading Channels
(Společnost pro radioelektronické inženýrství, 2011-06) Nikolic, Bojana; Djordjevic, Goran; Milosevic, Nenad
This paper presents the study of the effects of imperfect reference signal recovery on the bit error rate (BER) performance of dual-branch switch-and-stay combining (SSC) and multibranch selection combining (SC) receivers in a generalized - fading channel. The average BER of binary and quaternary phase shift keying (BPSK and QPSK) is derived under the assumption that the reference carrier signal is extracted from the received modulated signal. For SSC receiver the optimal switching threshold (in a minimum BER sense) is numerically evaluated. Hereby we determine and discuss the simultaneous influence of the average signal-to-noise ratio (SNR) per bit, fading severity, product phase-locked loop (PLL) bandwidthbit duration (B_LT_b), switching threshold of SSC and diversity order of SC on BER performance. The influence of B_LT_b in different channel conditions and modulation formats is pointed out. The numerical results are confirmed by computer simulations.
Evaluation and Investigation of the Delay in VoIP Networks
(Společnost pro radioelektronické inženýrství, 2011-06) Kyrbashov, Bakyt; Baronak, Ivan; Kovacik, Matus; Janata, Viktor
The paper is focused mainly on the delay problems, which considerably influence the final quality of connections in VoIP (Voice over IP) networks. The paper provides a detailed exploration of the nature and mechanisms of the delay. The main purpose of the investigation was an attempt to formulate a mathematical model of delay in the VoIP network and its subsequent analysis by laboratory data.

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