• Science of Emotion and Sensibility
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• v.24 no.2
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• pp.57-64
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• 2021

It has long been speculated that the visual system should use a coding strategy that takes advantage of statistical redundancies in images. But how such a coding strategy should manifest in neural responses has been less clear. Low-level image structure related to the power spectrum of natural images appears to be captured by a hard-wired efficient code in the retina of the fly and precortical structures like the LGN of cats that maximizes information content through the limited capacity channel of the optic nerve. But visual images are typically filled with higher-order structure beyond that captured by the power spectrum and visual cortex is not constrained by the same capacity limits as the optic nerve. Whether and how visual cortex can flexibly code for higher order redundancies is unknown. Here we show using psychophysical techniques that the neural response in early human visual cortex may be modulated by orientation redundancies in images such that a visual feature that is contained within a predictive pattern results in slower reaction times than a feature that deviates from a pattern, suggesting lower neural responses to predictable stimuli in the visual cortex. Our results point to a neural response in early visual cortex that is sensitive to global patterns and redundancies in visual images and is in marked contrast to standard models of cortical visual processing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1373-1391
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• 2022

We investigate mobile multiple-input multiple-output (MIMO) molecular communication via diffusion (MCvD) system which is consisted of two source nodes, two destination nodes and one relay node in the mobile three-dimensional channel. First, the combinations of decode-and-forward (DF) relaying protocol and network coding (NC) scheme are implemented at relay node. The adaptive thresholds at relay node and destination nodes can be obtained by maximum a posteriori (MAP) probability detection method. Then the mathematical expressions of the average bit error probability (BEP) of this mobile MIMO MCvD system based on DF and NC scheme are derived. Furthermore, in order to minimize the average BEP, we establish the optimization problem with optimization variables which include the ratio of the number of emitted molecules at two source nodes and the initial position of relay node. We put forward an iterative scheme based on block coordinate descent algorithm which can be used to solve the optimization problem and get optimal values of the optimization variables simultaneously. Finally, the numerical results reveal that the proposed iterative method has good convergence behavior. The average BEP performance of this system can be improved by performing the joint optimizations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.865-873
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• 2004

MPEG-2 Advanced Audio Coding(AAC) is widely used in the multi-channel audio compression standards. And it combines hi인-resolution filter bank prediction techniques, and Huffman coding algorithm to achieve the broadcast-quality audio level at very low data rates. The forward and inverse modified discrete transforms which are operated in the encoder and the decoder of the filter bank need many computations. In this paper, we propose suitable recursive structure at IMDCT processing for MPEG-2 AAC real-time decoder. We confirm the memory, the computation speed and complexity of the proposed structure.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.2
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• pp.102-108
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• 2017

Videos for 360-degree virtual reality (VR) systems have a large amount of data because they are made with several different videos from multiple cameras. To store the VR data in limited space or to transmit it through a channel with limited bandwidth, the data need to be compressed at a high ratio. This paper focuses on the compression efficiency of VR videos for good visual quality. Generally, 360-degree VR videos should be projected into the planer format to cope with modern video coding standards. Among various projection schemes, three typical schemes (equirectangular, line-cubic, and cross-cubic) are selected and compared in terms of compression efficiency and quality using various videos.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.7 s.349
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• pp.7-12
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• 2006

A simple 6-ary(3, 10) runlength-limited(RLL) code for a six-level optical recording channel is presented. The proposed code can be represented by a finite state diagram with six states. The code is given achieving coding density of $3.33bits/T_{min}$, which is 96.6% efficient.

• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.124-129
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• 2009

Although the maximum sum-rate capacity of multiple-input multiple output(MIMO) broadcast channels(BCs) can be achieved by dirty-paper coding(DPC), the results were obtained without fairness considerations in uncorrelated MIMO channels. In this paper, we propose new multiuser scheduling algorithms, which find a best user set for approaching the maximum sum-rate capacity while maintaining fairness among users. We analyze the performance of the proposed algorithms using zero-forcing dirty paper coding(ZF-DPC) in the correlated MIMO BCs for throughput and delay fairness, respectively. Numerical results demonstrate that a large time window can reduce the average throughput difference between users, but it increases head-of-line(HOL) delay jitters in the case of delay fairness.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.165-168
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• 2004

본 논문은 방송 및 통신 환경을 이용한 멀티채널 음향 재생 환경에서 다수 객체의 음상 정위를 보다 효과적이고 효율적으로 하기 위한 방법에 관한 것이다. 본 논문에서는 전송되는 정보의 양을 최소화 하면서도 재생되는 음향공간에서는 다수의 음향 객체들이 충실하게 재생되어 자연스러운 음향공간이 재현할 수 있는 방법을 제시하고가 한다. 기존 방법의 경우, 전송 선로를 통해 음원을 압축하여 전송하기 위해서는 먼저 멀티채널 신호를 합한 모노신호와 채널 신호사이의 음량차이(ICLD), 시간지연 차이(ICTD), 상관도(ICC)등을 전송하는 양귀단서 신호화 기술(Binaural Cue Coding)을 이용하고 있다. 본 논문에서는 멀티채널 음원을 분석하여, 음원의 가상 위치정보를 벡터적으로 표현하고, 이 위치벡터와 멀티채널 음원을 하나의 모노 음원으로 다운 믹스한 신호를 전송함으로써 전송 효율을 극대화 한 압축 재생 방법을 제시한다.

• Journal of Korea Multimedia Society
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• v.8 no.12
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• pp.1623-1630
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• 2005

Adaptive modulation and coding (AMC), which has a number of variation levels in accordance with the fading channel variation, is a promising technique for communication systems. In this paper, we present an AMC method using the cluster in OFDM system for bandwidth efficiency and performance improvement. The AMC schemes applied into each cluster or some clusters are determined by the minimum or the average SNR value among all the sub carriers within the corresponding cluster. It is important to find the optimal information on cluster because AMC performance can be varied according to the number and position of cluster. It is shown by computer simulation that the AMC method outperforms the fixed modulation in terms of bandwidth efficiency and its performance can be determined by the position and number of clusters.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.182-186
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• 2006

Previous approaches to sizing the carrier spacing for voice-oriented cellular systems have been based on the outage requirement. However, such a design paradigm needs to be changed as the performance of most upcoming cellular systems employing adaptive modulation and coding (AMC) techniques is more sensitive to throughput than outage. In this paper, we propose a novel approach to determining the carrier spacing which is based on a throughput criterion. The proposed method reflects well the characteristics of throughput-sensitive cellular systems that transport multimedia traffic. Numerical results show that our approach requires less carrier spacing, thus leading to more efficient spectrum utilization.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.12
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• pp.1792-1799
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• 1990

Two cases of block coded phase/frequncy modulations are investigated. minimum Euclidean distances are calculated as the function of modulation index h and rotation angle \ulcorner in the cases of 2-FSK/4-PSK and 2-FSK/8-PSK. Method of signal set partitioning is described, especially for the case of 2-FSK/8-PSK. The results are compared with S.I. Sayegh's work and shown better performance. For example, with simple parity check and repetition codes, we can get coding gain of 3 dB in the case of 2-FSK/4-PSK with block length n=4. We get 5.33 dB in the case of 2-FSK/8-PSK with n=4. And it is believed that we can get higher coding gain with proper combinations of block code and n-FSK/m-PSK type channel signal constellations.