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Oreste Andrisano - One of the best experts on this subject based on the ideXlab platform.

  • outage evaluation for slow frequency hopping mobile radio systems
    IEEE Transactions on Communications, 1999
    Co-Authors: Marco Chiani, Andrea Conti, Oreste Andrisano
    Abstract:

    In a shadowing-free environment, the improvement introduced by slow frequency-hopping (SFH) on a time-division multiple-access based mobile radio system can be taken into account by redefining the minimum carrier-to-interference ratio. This protection ratio, with SFH, is dependent on the transmission system, channel model, traffic, and frequency reuse parameters. In this paper, the above-mentioned analysis is used in order to investigate the capacity of a SFH mobile radio system, with reference to both the uplink and downlink, by taking into account a complete scenario, i.e., shadowing, fast fading, power control, antenna diversity, discontinuous transmission, and forward error correction with nonideal interleaving and sectorization. Outage probability is evaluated by a completely analytical methodology for the uplink, whereas the downlink requires a semianalytical approach to take users' positions into account. Comparison with a pure simulative approach is used to validate the results.

D. Chukurov - One of the best experts on this subject based on the ideXlab platform.

  • Performance of a TDMA portable radio link with a switching frequency synthesizer
    IEEE Global Telecommunications Conference GLOBECOM '91: Countdown to the New Millennium. Conference Record, 1991
    Co-Authors: A. Afrashteh, D. Chukurov
    Abstract:

    The authors present the performance of an experimental TDMA (time division multiple access) portable radio link with a switching single loop frequency synthesizer. The synthesizer, used as a local oscillator (LO), operates around 2 GHz with a 400 kHz step size and can switch over 20 MHz in less than 400 mu s. Performance of the TDMA radio link using WER (word error ratio) as a criterion was measured with the synthesizer switching frequencies between bursts at the transmitter. WER versus SNR (signal-to-noise ratio) shows small degradation, only 0.5 dB at WER of 10/sup -3/, due to the phase noise of the synthesizer signal. The phase noise values for an offset of 10 kHz and 100 kHz were -70 dBc/Hz and -90 dBc/Hz, respectively. Measurements indicated that the radio link performance showed only minor degradation when the synthesizer was switched 20 MHz only 400 mu s before transmitting a data burst. This permits a handset to switch to different channels than the channel of operation to measure signal quality for possible call-transfer once every 2 ms frame. >

  • Signal to interference performance for a TDMA portable radio link
    [1991 Proceedings] 41st IEEE Vehicular Technology Conference, 1991
    Co-Authors: A. Afrashteh, N.r. Sollenberger, D. Chukurov
    Abstract:

    The authors present measurement and simulation results of signal-to-interference ratio performance for a time-division multiple-access (TDMA) portable radio link The radio link transmits short TDMA bursts of only 82 symbols at 450 kb/s using 4-QAM (quadrature amplitude modulation). Demodulation is performed by a low-overhead digital coherent demodulator with two-branch selection diversity. The measured performance of the link is compared with the simulation results using word error ratio as a criterion. The results are also compared with signal-to-noise performance. To simulate the effect of portable movement, the measurements have been performed for several different fading rates. Desired and interfering TDMA burst signals were subjected to independent Rayleigh fading on two diversity branches. >

Marco Chiani - One of the best experts on this subject based on the ideXlab platform.

  • outage evaluation for slow frequency hopping mobile radio systems
    IEEE Transactions on Communications, 1999
    Co-Authors: Marco Chiani, Andrea Conti, Oreste Andrisano
    Abstract:

    In a shadowing-free environment, the improvement introduced by slow frequency-hopping (SFH) on a time-division multiple-access based mobile radio system can be taken into account by redefining the minimum carrier-to-interference ratio. This protection ratio, with SFH, is dependent on the transmission system, channel model, traffic, and frequency reuse parameters. In this paper, the above-mentioned analysis is used in order to investigate the capacity of a SFH mobile radio system, with reference to both the uplink and downlink, by taking into account a complete scenario, i.e., shadowing, fast fading, power control, antenna diversity, discontinuous transmission, and forward error correction with nonideal interleaving and sectorization. Outage probability is evaluated by a completely analytical methodology for the uplink, whereas the downlink requires a semianalytical approach to take users' positions into account. Comparison with a pure simulative approach is used to validate the results.

Linda S Schadler - One of the best experts on this subject based on the ideXlab platform.

  • dielectric constant and breakdown strength of polymer composites with high aspect ratio fillers studied by finite element models
    Composites Science and Technology, 2013
    Co-Authors: Zepu Wang, Keith J Nelson, Henrik Hillborg, Su Zhao, Linda S Schadler
    Abstract:

    Abstract A finite element model was used to study the dielectric constant and breakdown strength of polymer composite filled with high aspect ratio fillers. The impact of composite microstructure and filler aspect ratio on the dielectric properties was investigated. The results were used to explain the experimental data for BaTiO 3 fiber filled poly(dimethyl siloxane) published previously. The effect of filler shape, aspect ratio distribution, curvature, grain boundary and alignment on the composite permittivity was studied. A model was proposed to correlate the composite microstructure, the electric field distribution in the polymer matrix, and the dielectric breakdown strength of composites.

C Charoenpong - One of the best experts on this subject based on the ideXlab platform.

  • a continuous flow isotope ratio mass spectrometry method for high precision determination of dissolved gas ratios and isotopic composition
    Limnology and Oceanography-methods, 2014
    Co-Authors: C Charoenpong, Laura A Bristow, Mark A Altabet
    Abstract:

    Dissolved gas ratios and isotopic compositions provide essential information about the biological and physical mechanisms influencing N2, O2, and Ar in aquatic systems. Current methods available are either limited by overall cost, labor-intensive sample collection and analysis, or insufficient precision. Here, we present a new highly accurate and robust method for sample collection and subsequent simultaneous measurement of the dissolved gas ratios (N2/Ar and O2/Ar) and isotopic compositions (δ15N2 and δ18O2) in seawater. The relatively simple sampling procedure using low cost materials enables collection of hundreds to more than a thousand discrete samples on a single research cruise. Samples can be preserved and stored at room temperature and maintain their integrity for many months. Laboratory analysis employs an on-line extraction system coupled to a multi-collector isotope ratio mass spectrometer (IRMS). A continuous flow of He carrier gas completely degasses the sample, and passes through the preparation and purification system before entering the IRMS for analysis. The use of this continuous He carrier permits short analysis times (less than 8 min per sample) as compared with current high-precision methods. In addition to reference gases, calibration is achieved using air-equilibrated water standards of known temperature and salinity. Assessment of reference gas injections, air equilibrated standards, as well as samples collected in the field shows the accuracy and precision of this new method to be equal to or better than current standard techniques.