• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.7A
• /
• pp.628-638
• /
• 2005

The analysis of maximum diversity order and coding gain for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems over time-and frequency-selective (or doubly-selective) channels is addressed in this paper. A novel channel time-space correlation function is developed given the spatially correlated doubly-selective Rayleigh fading channel model. Based on this channel-model assumption, the upper-bound of pairwise error probability (PEP) for MIMO-OFDM systems is derived under the maximum likelihood (ML) detection. For a certain space-frequency code, we quantify the maximum diversity order and deduce the expression of coding gain. In this wort the impact of channel time selectivity is especially studied and a new definition of time diversity is illustrated correspondingly

• ETRI Journal
• /
• v.25 no.4
• /
• pp.231-237
• /
• 2003

We derive and analyze the exact closed-form expression for the average bit error probability (BEP) of M-ary square quadrature amplitude modulation (QAM) for diversity reception in frequency-nonselective Nakagami fading. A maximal ratio combining (MRC) diversity technique with independent or correlated fading cases are considered. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The presented new expressions offer a convenient way to evaluate the performance of M-ary square QAM with an MRC diversity combiner for various cases of practical interest.

• Proceedings of the IEEK Conference
• /
• 2002.06d
• /
• pp.33-36
• /
• 2002

Multiple Description Coding(MDC) is a technique used to obtain two or more (often correlated) descriptions of a source, which are transmitted over different channels to receiver. Two descriptions of the source support two levels of reconstruction quality. When all the descriptions are received and used in the reconstruction, the source should be reconstructed with acceptable quality. In this work, we consider Multiple Description Scalar Quantizer(MDSQ) to wavelet transform domain. Conventional MDSQ schemes in wavelet domain considered description with equal weights at each sub-bands after quantization. But each sub-bands is unequal contribution to whole image quality. Therefore, we experiment the multiple description with unequal weight in each sub-bands.

• Journal of Communications and Networks
• /
• v.9 no.2
• /
• pp.150-158
• /
• 2007

We consider channel-coded multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) transmission and obtain a condition on its signal for it to attain the maximum diversity and coding gain. As this condition may not be realizable, we propose a suboptimal design that employs an orthogonal transform and a space-frequency interleaver between the channel coder and the multi-antenna OFDM transmitter. We propose a corresponding receiving method based on block turbo equalization. Attention is paid to some detailed design of the transmitter and the receiver to curtail the computational complexity and yet deliver good performance. Simulation results demonstrate that the proposed transmission technique can outperform the conventional coded MIMO OFDM and the MIMO block single-carrier transmission with cyclic prefixing.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.1261-1263
• /
• 2003

Based on twelve observational stations low meteorological visibility (LMV) data during November 2002 to April 2003, the spatial distribution of LMV over Hongkong area (113.8$^{\circ}$ E-114.4$^{\circ}$ E, 22.1$^{\circ}$ N-22.4$^{\circ}$ N) is studied, using a PCA method. Optical spectrum of NOAA-16 associated with LMV shows that the significant effect factors correlated with LMV in the leading mode are the difference or rate between the visible and near-IR channels and single visible channel. A successful retrieval of LMV is done and a regression equation with a multiple correlation coefficient of 0.67 is obtained.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.10A
• /
• pp.1521-1528
• /
• 2000

In this paper we analyze the performance of a DS/CDMA system in LEO mobile satellite channels. The channel uses the Extended Suzuki model which is the product of a Rician distribution having a LOS component and a lognormal distribution due to shadowing. We assume that the signal transmitted from the satellite to the mobile undergoes the same fading for the whole coverage of signal's beam. The average bit error probabilities of double coverage system is calculated in this paper. The interference resulting from the reference satellite is calculated for mobile located in the middle of the double coverage region whereas the additive interference from next-satellite is included for mobile located in the edge of the double coverage region. The performance of the mobile's receiving signal is dependent on shadowing and the interference of the next-satellite. We can obtain an obtain an improved average bit error probability by using dual diversity over the conventional correlated receiver for similar shadowing conditions in the coverage area of the satellite channel.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.29.1-29.1
• /
• 2021

There have been many studies aiming to reveal the origins of the star-gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We explore the properties, origins, and lifetimes of the star-gas misalignment using Horizon-AGN, a large-volume cosmological simulation. First, the misalignment fraction shows a strong anti-correlation with the kinematic morphology (V/sigma) and the cold gas fraction of the galaxy. This result is consistent with the result of integral field spectroscopy observations. Second, we have identified four main formation channels of misalignment and quantified their level of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution including smooth accretion from neighboring filaments (21%). Third, the decay timescale of the misalignment is strongly linked with the kinematic morphology of the galaxy: early-type galaxies (2.28 Gyr) tend to have a longer misalignment lifetime than LTGs (0.49 Gyr). We also found that the morphology and cold gas fraction are both and independently anti-correlated with the misalignment lifetime.

• Asia pacific journal of information systems
• /
• v.31 no.3
• /
• pp.277-295
• /
• 2021

This paper examines the features that make a YouTube channel attractive to users. Considering that drawing users' attention is challenging on this platform, where voluminous amounts of videos are available, it is crucial to identify the factors that make users intend to subscribe to a YouTube channel. In this study, we used an online survey to collect data from 1125 respondents and an SEM model using Smart PLS 3.2.8 to analyze it. The results show that integrity and familiarity with a YouTube channel are positively correlated with trust in its creator, which leads to subscribing to the YouTube channel; value and accuracy also positively affect intention to subscribe to a YouTube channel via trust in content. This study enriches the field of research about trust in the creator and trust in content.

• Journal of IKEEE
• /
• v.11 no.3
• /
• pp.108-116
• /
• 2007

This paper proposed an analyzable parameter and its analytic method to provide more accurate information than currently employed 4 channels system which uses pulse wave velocity (PWV) information of the volume pulse wave measured from 4 arterial channels for the characterization of arterial vessel. In order to verify the volume pulse waves on 4 sites were simultaneously acquired subjects aged from 12 to 81 years old. and the proposed parameters were extracted from time (UT) was then compared with blood pressure. Then, the regression analyses were done relationships among the proposed parameter and others, such as aging, pulse transit time pressure (BP). The followings are the results of linear regression analysis of the proposed parameter for total 50 normal subjects. We selected any two subjects (58 years and 27 years) and measured PPG (photoplethysmogram) and BP of before and after exercise. The coefficient of correlations between BP and UT observed was -0.928 for 50 years subject, and -0.922 for 20 years subject. For total 50 normal subjects, in case of correlation between the pulse transit time and BP, the result showed -0.170 on left side and -0.233 on right side, and the coefficient value of correlation between the pulse transit time and UT was -0.607 on left side and -0.510 on right side. UI is strongly correlated with the pulse transit time than BP. Hence, we believe that the proposed parameter is related with the index of arterial stiffness.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.1
• /
• pp.11-18
• /
• 2012

In this paper, we propose a novel equal-gain differential precoding scheme utilizing temporal correlation of channels. The conventional differential precoding schemes only quantize a part of channel space not the whole channel space, so that it virtually increases codebook size which enhances the system capacity. But the conventional differential schemes increase peak-to-average power ratio (PAPR) without preserving equal-gain transmission. This paper proposes the design method of equal-gain differential precoding scheme and analyzes the performances of the proposed equal-gain precoding scheme. Monte-Carlo simulations verify that the proposed scheme has an advantage of 1dB to obtain the same system capacity with the same amount of feedback information compared with the conventional LTE schemes, with showing very low PAPR property.