• Journal of Communications and Networks
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• v.10 no.4
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• pp.412-421
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• 2008

We observe simultaneous transmission of relay stations (RSs) allowed in current IEEE 802.16j draft standard for multi-hop relay networks may involve severe interference among the RSs, hence leading to throughput degradation. Allowing only 1/3 of the RSs to simultaneously transmit instead of 1/2 RSs as in the current draft standard reduces the interference but results in reduced throughput. To remedy this problem, we devise schemes to incorporate network coding at link-layer level (decode-and-forward) into the simultaneous transmission of RSs. Data movement is rearranged to maximize coding gain. Formula is derived to dictate exact movement of packets traveling between base station (BS) and mobile stations (MSs) via intermediate RSs. The frame structure in the current IEEE 802.16j draft standard does not allow broadcast needed for network coding. We devise a new frame structure which supports the broadcast. A new R-MAP (pointers to the burst data) is introduced to implement the broadcast. Since our new frame structure is used only for BS to RS or RS to RS communication, our schemes retain backward compatibility with legacy MSs based on IEEE 802.16e standard. Simulation based on simple configuration of RSs shows considerable improvement in terms of system throughput and round trip delay. For a 4-hop relay network with 1 BS and 4 RSs with symmetric traffic in uplink (UL) and downlink (DL), throughput is improved by 49% in DL and by 84% in UL traffic compared with IEEE 802.16j draft standard under the assumption that omni-directional antennae are used in BS and RSs.

• The Journal of the Acoustical Society of Korea
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• v.15 no.3E
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• pp.37-44
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• 1996

A new method for efficient modeling of the Head-Related Transfer Functions(HRTF's) without loss of any directional information is proposed. In this paper, the HRTF's were empirically measured in a real room and modeled as the ARMA models with common AR coefficients and different MA coefficients. To assess the validity of the proposed ARMA model, psychophysical tests show that the proposed ARMA model, in comparison with the conventional MA model, requires a small number of parameters to represent empirical HRTF's and improves the back-to-front confusions in sound-field localization. Thus, significant simplifications in the implementations of sound-field synthesis systems could be obtained by using the proposed ARMA model.

• Journal of Broadcast Engineering
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• v.23 no.4
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• pp.559-573
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• 2018

Recently, one of the most actively applied image media in the most fields such as virtual reality (VR) is omni-directional or panorama image. This image is generated by stitching images obtained by various methods. In this process, it takes the most time to extract keypoints necessary for stitching. In this paper, we analyze the parameters involved in the extraction of SIFT keypoints with the aim of reducing the computation time for extracting the most widely used SIFT keypoints. The parameters considered in this paper are the initial standard deviation of the Gaussian kernel used for Gaussian filtering, the number of gaussian difference image sets for extracting local extrema, and the number of octaves. As the SIFT algorithm, the Lowe scheme, the originally proposed one, and the Hess scheme which is a convolution cascade scheme, are considered. First, the effect of each parameter value on the computation time is analyzed, and the effect of each parameter on the stitching performance is analyzed by performing actual stitching experiments. Finally, based on the results of the two analyses, we extract parameter value set that minimize computation time without degrading.

• Journal of Broadcast Engineering
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• v.16 no.4
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• pp.657-668
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• 2011

Along with the development of communication technology, DTV is gradually evolving into media that provide diverse services and information. This study is related with remote controls that control DTV interfaces and assessed the usability of remote pointing device. To this end, pointing devices using three different interaction methods that have been attempted recently by the industry were selected to conduct empirical experiments. The usability assessment was conducted centering on the existing directional task on straight tracks presented in ISO 9241-Part 9 and the steering tunnel task on curved tracks proposed in this study. The measurement variables included movement time, accuracy, throughput, subjective satisfaction and user behaviors. Based on the results of the assessment, in the case of movements on straight tracks, the GyroPoint method showed better implementing time but lower accuracy compared to the Hall Mouse and OFN methods while in the case of assessment on curved tracks, all of the GyroPoint method, Hall Mouse and OFN methods showed excellent results on both implementing time and accuracy. Besides, differences in efficiency and subjective satisfaction were shown among individual pointing devices. Based on these results, it is considered that individual pointing methods have different advantageous and disadvantageous characteristics. In this study, the usability of remote control pointing methods was assessed and diagnosed reflecting environments where DTVs are used through assessments considering the aspect of straight tracks along with curved tracks. Among others, this study is considered to be meaningful in that it provides assessment criteria and basic data for the development of remote controls suitable for the evolving DTV environments.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.817-827
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• 2008

The terrestrial-digital multimedia broadcasting(T-DMB) is now provided for the public service and the number of receivers reaches 15 million at the present of August 2008. The service of T-DMB itself has been succeeded in the presence. It is however remained as a supplementary role of stationed TV. It is necessary to find an additional business model as a new media to acquire surplus escaping from the deficit of the present T-DMB service. In the present paper, data service of T-DMB is proposed as candidate of such solution. Especially, TTI(Traffic and Travel Information) service is proposed as a killer application using TPEG(Transport Protocol Experts Group). At present, TPEG has not been so popular in the sense of various user satisfaction. Thus the variety of service including bi-directional service using DMB2.0 as in the sphere of Web2.0 is necessary for the service providers. In the paper, the restriction of TPEG-POI(Point of Interest) application service using the conventional mobile communication infrastructure is indicated. To overcome such restriction, TPEG-UCM(User Created Message) application service model using individual bi-directional media which is initiated and interacting by the users is proposed. In the experiment, the application program shows the usability of the proposed method so that the implementation results show its operability.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.108-121
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• 2012

As Scalable Video Coding (SVC) is a video compression standard extended from H.264/AVC, it is a way to provide scalability in terms of temporal, spatial and quality. Although the compression efficiency of SVC is increased due to the scalability in many aspect, it is essential to reduce the complexity in order to efficiently use because the complexity is relatively increased. To reduce the complexity of SVC in the paper, we propose fast mode decision algorithm to reduce the complexity of encoding process using direction information of B-picture by efficiently performing inter-layer prediction. The proposed algorithm is a fast mode decision algorithm that makes different from detection mode number of forward and backward, bi-direction in the way using best mode of base-layer up-sampled after simply SKIP mode detection using the direction information of best mode of base-layer up-sampled. The experimental results show that the proposed algorithm approach can achieve the maximum computational time saving about 53% with almost no loss of rate distortion (RD) performance in the enhancement layer.

• Journal of Broadcast Engineering
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• v.24 no.3
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• pp.463-471
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• 2019

This paper proposes a method for reducing the complexity of LIC (Local Illuminance Compensation) for bi-directional inter prediction. The LIC performs local illumination compensation using neighboring reconstruction samples of the current block and the reference block to improve the accuracy of the inter prediction. Since the weight and offset required for local illumination compensation are calculated at both sides of the encoder and decoder using the reconstructed samples, there is an advantage that the coding efficiency is improved without signaling any information. Since the weight and the offset are obtained in the encoding prediction step and the decoding step, encoder and decoder complexity are increased. This paper proposes two methods for low complexity LIC. The first method is a method of applying illumination compensation with offset only in bi-directional prediction, and the second is a method of applying LIC after weighted average step of reference block obtained by bidirectional prediction. To evaluate the performance of the proposed method, BD-rate is compared with BMS-2.0.1 using B, C, and D classes of MPEG standard experimental image under RA (Random Access) condition. Experimental results show that the proposed method reduces the average of 0.29%, 0.23%, 0.04% for Y, U, and V in terms of BD-rate performance compared to BMS-2.0.1 and encoding/decoding time is almost same. Although the BD-rate was lost, the calculation complexity of the LIC was greatly reduced as the multiplication operation was removed and the addition operation was halved in the LIC parameter derivation process.

• Journal of Korea Multimedia Society
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• v.7 no.10
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• pp.1452-1463
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• 2004

The requirement of automatic video summary is increasing as bi-directional broadcasting contents and various user requests and preferences for the bi -directional broadcast environment are increasing. Automatic video summary is needed for an efficient management and usage of many contents in service provider as well. In this paper, we propose a method to generate a content-based summary of linguistic educational videos automatically. First, shot-boundaries and keyframes are generated from linguistic educational video and then multiple(low-level) visual features are extracted. Next, the semantic parts (Explanation part, Dialog part, Text-based part) of the linguistic educational video are generated using extracted visual features. Lastly the XMI- document describing summary information is made based on HieraTchical Summary architecture oi MPEG-7 MDS (Multimedia I)escription Scheme). Experimental results show that our proposed algorithm provides reasonable performance for automatic summary of linguistic educational videos. We verified that the proposed method is useful ior video summary system to provide various services as well as management of educational contents.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.1-8
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• 2006

In this paper, we propose carrier phase synchronization algorithm which are base on turbo coded system for DVB-RCS. There have been two categories of phase estimator, single estimator outside turbo code decoder and multiple estimators inside turbo code decoder. In single estimator, we use the estimation algorithm that ML(Maximum Likelihood) and LMS(Least Mean Square), also three different soft decision methods are proposed. Multiple estimator apply PSP(Per Survivor Processing) algorithm additionally. We compared performance between single estimator and Multiple estimator in AWGN channel. We presented the two methods of PSP algorithm for performance elevation. First is the Bi-directional channel estimation and second is binding method.

• Journal of Broadcast Engineering
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• v.1 no.2
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• pp.118-132
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• 1996

This paper proposes a wavelet transform- based image compression method using the energy distribution. The proposed method Involves two steps. First, we use a wavelet transform for the subband decomposition. The original image Is decomposed into one low resolution subimage and three high frequency subimages. Each high frequency subimages have horizontal, vertical, and diagonal directional edges. The wavelet transform is luther applied to these high frequency subimages. Resultant transformed subimages have different energy distributions corresponding to different orientation of the high pass filter. Second, for higer compression ratio and computational effciency, we discard some subimages with small energy. The remaining subimages are encoded using either DPCM or quantization followed by entropy coding. Experimental results show that the proposed coding scheme has better performance in the peak signal to noise ratio(PSNR) and higher compression ratio than conventional image coding method using the wavelet transform followed by the straightforward vector quantization.