The Experts below are selected from a list of 30 Experts worldwide ranked by ideXlab platform
G M Zaslavsky - One of the best experts on this subject based on the ideXlab platform.
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wave analysis of ray chaos in underwater acoustics
Chaos, 1999Co-Authors: Bala Sundaram, G M ZaslavskyAbstract:The dispersion of a wave Packet in an acoustic medium is considered in the paraxial wave approximation, where the effective potential, due to variation of the speed of propagation, varies both with depth and propagation distance. The analysis of the resulting parabolic equation, similar to the Schrodinger equation, clearly demonstrates the role of ray chaos in enhancing the dispersion of the Initial Packet. However, wave coherence effects are also seen that suppress the effects of the ray chaos in a manner analogous to the effects of quantum chaos.
M Sawahashi - One of the best experts on this subject based on the ideXlab platform.
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experimental evaluation of time diversity effect in hybrid arq considering space and path diversity for downlink ofdm based broadband radio access
IEICE Transactions on Communications, 2009Co-Authors: Nobuhiko Miki, Hiroyuki Atarashi, M Sawahashi, Kenichi Higuchi, Masao NakagawaAbstract:This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based Packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual Packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the Initial Packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.
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effect of time diversity in hybrid arq considering space and path diversity for vsf ofcdm downlink broadband wireless access
Personal Indoor and Mobile Radio Communications, 2004Co-Authors: Nobuhiko Miki, Hiroyuki Atarashi, M SawahashiAbstract:The paper investigates the effect of time diversity derived from hybrid automatic repeat request (ARQ) with Packet combining considering space and path diversity schemes on variable spreading factor orthogonal frequency and code division multiplexing (VSF-OFCDM) Packet wireless access in a downlink broadband multipath fading channel based on laboratory and field experiments. The results show that, for a fixed modulation and channel coding scheme (MCS), time diversity derived from hybrid ARQ is effective in reducing the required received signal-to-interference-plus-noise power ratio (SINR) according to an increase in the number of transmissions, M, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity by a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain derived through time diversity is almost saturated at M=4 in chase combining and M=2 in incremental redundancy, since the improvement in the residual Packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the Initial Packet transmission arising from appropriately selecting the optimum MCS in AMC.
Nobuhiko Miki - One of the best experts on this subject based on the ideXlab platform.
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experimental evaluation of time diversity effect in hybrid arq considering space and path diversity for downlink ofdm based broadband radio access
IEICE Transactions on Communications, 2009Co-Authors: Nobuhiko Miki, Hiroyuki Atarashi, M Sawahashi, Kenichi Higuchi, Masao NakagawaAbstract:This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based Packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual Packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the Initial Packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.
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effect of time diversity in hybrid arq considering space and path diversity for vsf ofcdm downlink broadband wireless access
Personal Indoor and Mobile Radio Communications, 2004Co-Authors: Nobuhiko Miki, Hiroyuki Atarashi, M SawahashiAbstract:The paper investigates the effect of time diversity derived from hybrid automatic repeat request (ARQ) with Packet combining considering space and path diversity schemes on variable spreading factor orthogonal frequency and code division multiplexing (VSF-OFCDM) Packet wireless access in a downlink broadband multipath fading channel based on laboratory and field experiments. The results show that, for a fixed modulation and channel coding scheme (MCS), time diversity derived from hybrid ARQ is effective in reducing the required received signal-to-interference-plus-noise power ratio (SINR) according to an increase in the number of transmissions, M, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity by a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain derived through time diversity is almost saturated at M=4 in chase combining and M=2 in incremental redundancy, since the improvement in the residual Packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the Initial Packet transmission arising from appropriately selecting the optimum MCS in AMC.
Dmitry G. Blinov - One of the best experts on this subject based on the ideXlab platform.
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effect of diffusion on slowing the velocity of a bell shaped wave in slow axonal transport
International Communications in Heat and Mass Transfer, 2010Co-Authors: A. V. Kuznetsov, Andriy A. Avramenko, Dmitry G. BlinovAbstract:Abstract This paper models transport of organelles by slow axonal transport utilizing the stop-and-go hypothesis, which postulates that in slow axonal transport the motion of organelles does not occur continuously; instead, organelles move along microtubules (MTs) alternating between short periods of rapid movement, short on-track pauses, and prolonged off-track pauses, when they temporarily disengage from MTs. The model considers six kinetic states of organelles: anterogradely moving state, retrogradely moving state, anterogradely pausing state, retrogradely pausing state, off-track anterograde state, and off-track retrograde state. The paper extends the existing model of slow axonal transport by accounting for the diffusivity of off-track organelles and investigates how the diffusivity of these organelles affects the amplitude, velocity, and rate of change of the variance of the bell-shaped wave which describes the probability density function (PDF) corresponding to the ratio of the chance of finding an organelle within an infinitesimal interval in the axon to the length of this interval. The velocity of this wave characterizes the average effective velocity (calculated including pauses) of an organelle in slow axonal transport while the rate of change of the variance characterizes the rate of spread of the Initial Packet of organelles transported in the axon. The goal of this research is not only to develop a more accurate transport model, but also to understand fundamentally the effects of diffusion on slow axonal transport. It is demonstrated that diffusion decreases the amplitude of the wave and increases the rate of its spread but does not affect wave's velocity.
Bala Sundaram - One of the best experts on this subject based on the ideXlab platform.
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wave analysis of ray chaos in underwater acoustics
Chaos, 1999Co-Authors: Bala Sundaram, G M ZaslavskyAbstract:The dispersion of a wave Packet in an acoustic medium is considered in the paraxial wave approximation, where the effective potential, due to variation of the speed of propagation, varies both with depth and propagation distance. The analysis of the resulting parabolic equation, similar to the Schrodinger equation, clearly demonstrates the role of ray chaos in enhancing the dispersion of the Initial Packet. However, wave coherence effects are also seen that suppress the effects of the ray chaos in a manner analogous to the effects of quantum chaos.