The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Youngwook Ko - One of the best experts on this subject based on the ideXlab platform.
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TCM for OFDM-IM
IEEE Wireless Communications Letters, 2018Co-Authors: Jinho Choi, Youngwook KoAbstract:Orthogonal frequency division multiplexing (OFDM) with Index modulation (IM) is a multicarrier transmission technique for frequency-selective fading channels. Although it is energy and spectral efficient, its performance may not be satisfactory as some active subcarriers can be suppressed by fading. In this letter, we consider trellis coded modulation (TCM) for OFDM-IM in order to improve the detection performance of active subcarriers by increasing the Hamming distance between Index symbols. We devise mapping rules for TCM for two cases and it is shown that the diversity order can be improved, which results in a lower probability of Index Error.
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The BER Analysis of MRC-Aided Greedy Detection for OFDM-IM in Presence of Uncertain CSI
IEEE Wireless Communications Letters, 2018Co-Authors: Thien Van Luong, Youngwook KoAbstract:This letter investigates the bit Error rate (BER) performance of orthogonal frequency division multiplexing Index modulation, employing the maximal ratio combining-based low-complexity greedy detector (MRC-GD) and the PSK modulation. For performance analysis, we derive tight expressions for both Index Error probability (IEP) and BER, taking into account channel state information (CSI) uncertainty. This provides insight into various impacts of CSI uncertainty on the diversity gain and Error floor of the IEP and the BER, respectively. We clearly show that under imperfect CSI, the MRC-aided GD can perform like the MRC-maximum likelihood detector, at lower complexity. Finally, simulation results are presented to verify the accuracy of derived expressions and the theoretical analysis.
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Cooperative OFDM-IM Relay Networks With Partial Relay Selection Under Imperfect CSI
IEEE Transactions on Vehicular Technology, 2018Co-Authors: James Crawford, Youngwook KoAbstract:In this paper, we investigate the performance of cooperative orthogonal frequency division multiplexing with Index modulation (OFDM-IM) with the low complexity greedy detection (GD). In particular, we propose a novel partial relay selection scheme whose search criteria are designed to exploit the IM subcarriers. To provide low-complexity receiver, we further examine the energy-sensing based GD design for the cooperative OFDM-IM. For the performance analysis, we derive novel upper bound and approximate closed form solutions for both the average Index Error probability and the average symbol Error probability over Nakagami-m fading channels with imperfect channel state information (CSI) at the relays and destination. Unlike the information theoretical works, in presence of positive detection Error in the relays, the derived expressions provide a useful insight into the Error performance of cooperative OFDM-IM under various fading conditions. The numerical and simulation results clearly present that the proposed scheme harmonizing partially selected relays and their IM subcarriers with GD can outperform the benchmark schemes, under uncertain CSI, at reduced complexity.
Jinho Choi - One of the best experts on this subject based on the ideXlab platform.
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TCM for OFDM-IM
IEEE Wireless Communications Letters, 2018Co-Authors: Jinho Choi, Youngwook KoAbstract:Orthogonal frequency division multiplexing (OFDM) with Index modulation (IM) is a multicarrier transmission technique for frequency-selective fading channels. Although it is energy and spectral efficient, its performance may not be satisfactory as some active subcarriers can be suppressed by fading. In this letter, we consider trellis coded modulation (TCM) for OFDM-IM in order to improve the detection performance of active subcarriers by increasing the Hamming distance between Index symbols. We devise mapping rules for TCM for two cases and it is shown that the diversity order can be improved, which results in a lower probability of Index Error.
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Noncoherent OFDM-IM and Its Performance Analysis
IEEE Transactions on Wireless Communications, 2018Co-Authors: Jinho ChoiAbstract:In conventional orthogonal frequency division multiplexing (OFDM) with Index modulation (OFDM-IM), the active subcarriers can convey information bits by modulated symbols as well as their indices. To detect modulated symbols, coherent detection is usually considered, which requires the channel state information (CSI) estimation for all subcarriers at a receiver. In OFDM-IM, however, since only a fraction of subcarriers are active, the overhead for pilot transmissions through all subcarriers to allow the receiver to estimate the CSI could be excessive, in particular, under a fast fading environment. To avoid this difficulty, we consider noncoherent OFDM-IM, where only the indices of active subcarriers are used to convey information bits. For a better performance, a transmit diversity scheme is also studied. We derive a closed-form expression for the probability of Index Error when no transmit diversity is considered under frequency-selective Rayleigh fading. We also derive an upper-bound when the transmit diversity scheme is employed. From the upper-bound, the diversity order is also clearly shown.
James Crawford - One of the best experts on this subject based on the ideXlab platform.
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Cooperative OFDM-IM Relay Networks With Partial Relay Selection Under Imperfect CSI
IEEE Transactions on Vehicular Technology, 2018Co-Authors: James Crawford, Youngwook KoAbstract:In this paper, we investigate the performance of cooperative orthogonal frequency division multiplexing with Index modulation (OFDM-IM) with the low complexity greedy detection (GD). In particular, we propose a novel partial relay selection scheme whose search criteria are designed to exploit the IM subcarriers. To provide low-complexity receiver, we further examine the energy-sensing based GD design for the cooperative OFDM-IM. For the performance analysis, we derive novel upper bound and approximate closed form solutions for both the average Index Error probability and the average symbol Error probability over Nakagami-m fading channels with imperfect channel state information (CSI) at the relays and destination. Unlike the information theoretical works, in presence of positive detection Error in the relays, the derived expressions provide a useful insight into the Error performance of cooperative OFDM-IM under various fading conditions. The numerical and simulation results clearly present that the proposed scheme harmonizing partially selected relays and their IM subcarriers with GD can outperform the benchmark schemes, under uncertain CSI, at reduced complexity.
A. Sugita - One of the best experts on this subject based on the ideXlab platform.
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Estimation of waveguide phase Error in silica-based waveguides
Journal of Lightwave Technology, 1997Co-Authors: S. Suzuki, A. SugitaAbstract:A new estimation method is proposed in order to clarify waveguide phase Error factors. Using the proposed method, it is possible to analyze such factors as core size Error and refractive Index Error, which cause optical phase Error in waveguides. This method is applied to silica-based waveguides to estimate the waveguide phase Error. This revealed an average core size Error of 2.1/spl times/10/sup -3/ /spl mu/m and an average refractive Index Error of 1.9/spl times/10/sup -6/. Finally, based on the measured phase Error values, the optimum arrayed-waveguide grating (AWG) configuration is considered with a view to achieving low crosstalk.
Oğuz Kucur - One of the best experts on this subject based on the ideXlab platform.
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ISWCS - Performance of spatial modulation schemes using transmit antenna selection with imperfect feedback
2017 International Symposium on Wireless Communication Systems (ISWCS), 2017Co-Authors: Ahmet Faruk Coşkun, Oğuz KucurAbstract:This paper investigates the effects of feedback Errors on the performance of transmit antenna selection (TAS)-aided spatial modulation (SM) schemes, and provides insightful view-points for assessing and comparing the performance of TAS/SM schemes to other open- and closed-loop spatial multiplexing and diversity schemes in case of feedback imperfections. Average bit Error rate performances of TAS/SM schemes for M-ary digital modulations are examined via both Monte Carlo simulations and numerical evaluation of semi-analytical derivations. Additionally, asymptotic behaviour of the antenna Index Error probability of TAS/SM schemes has been examined in order to sketch the overall diversity order of the average bit Error rate performances.
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Performance of spatial modulation schemes using transmit antenna selection with imperfect feedback
2017 International Symposium on Wireless Communication Systems (ISWCS), 2017Co-Authors: Ahmet Faruk Coşkun, Oğuz KucurAbstract:This paper investigates the effects of feedback Errors on the performance of transmit antenna selection (TAS)-aided spatial modulation (SM) schemes, and provides insightful view-points for assessing and comparing the performance of TAS/SM schemes to other open- and closed-loop spatial multiplexing and diversity schemes in case of feedback imperfections. Average bit Error rate performances of TAS/SM schemes for M-ary digital modulations are examined via both Monte Carlo simulations and numerical evaluation of semi-analytical derivations. Additionally, asymptotic behaviour of the antenna Index Error probability of TAS/SM schemes has been examined in order to sketch the overall diversity order of the average bit Error rate performances.
