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Daejeon, South Korea

Kim H.-C.,Comesta Inc. | Lim C.-S.,Comesta Inc. | Lee C.-S.,Hanbat National University | Choi J.-H.,Korea Polytechnic University
Journal of Communications | Year: 2016

As the use of UAV (Unmanned Aerial Vehicle) such as drone has been increased recently, aerial video shooting technology and surveillance system began to attract global attention. The video surveillance system using an UAV requires high speed wireless transmission technology to obtain high resolution video images in real-time under poor on-air channel environment, accurate positioning trace technology to identify the actual position of the shooting area, and remote control technology for safe flight of an UAV. In this paper, solutions for two important technical issues that should be resolved and coupled in VSSU (Video Surveillance System using UAV) were suggested. One is a RTPA (Real-Time Position Analysis) method to estimate shooting location and area of an interesting zone. Another one is high-speed transmission method for wireless data-link to minimize distortion of valid images information even in poor wireless channel environment. The suggested high-speed transmission method provided same or higher transmission quality than existing wireless data-link transmission method, and more flexible data size to transmit both of mass video data and small control data. Also, the demanded performance of suggested methods was verified through simulation and actual realization. To analyze performance of the RTPA method, actual location and shooting area about shooting images were measured in three different locations by using Quad-copter. And then both location and shooting area of its predictability region were calculated based on GPS (Global Positioning System) information and camera status information by applying RTPA method. The result of this study can be applied to various surveillance applications. © 2016 Journal of Communications. Source


Ahmed S.,Chonbuk National University | Zhang M.,Chonbuk National University | Kim S.,Chonbuk National University | Kim W.-Y.,Comesta Inc. | Cho Y.-H.,Comesta Inc.
International Conference on ICT Convergence | Year: 2013

In this letter, we present some aspects of bit interleaving schemes applicable for turbo codes with block and convolutional codes as their component codes. A bit interleaving scheme across inter-codewords can be used to increase the performance of the codes when a block of correlated channel information exits in a codeword. We present an efficient bit interleaving scheme that can maximize the time diversity of the codeword, especially for block turbo codes. © 2013 IEEE. Source


Zhang M.,Chonbuk National University | Kim S.,Chonbuk National University | Kim W.-Y.,Comesta Inc. | Cho Y.-H.,Comesta Inc.
Proceedings of the International Symposium on Consumer Electronics, ISCE | Year: 2014

We propose an efficient soft iterative decoding scheme with early termination algorithm for raptor codes. In the proposed scheme, the performance is enhanced by adopting iterative decoding, both in each inner and outer code and in the concatenated code itself between the inner and outer codes. At the same time, the complexity is reduced by applying an efficient early termination algorithm. Simulation results show that our proposed method can achieve a large amount of complexity reduction without any performance degradation. © 2014 IEEE. Source


Zhang M.,Chonbuk National University | Kim S.,Chonbuk National University | Chang J.Y.,Comesta Inc. | Kim W.-Y.,Comesta Inc.
IET Communications | Year: 2015

Raptor codes are a class of rateless codes that were originally designed for binary erasure channels. To enhance their performance, multiple soft iterative loops can be employed in the decoder. In this study, the authors propose a method to construct modified Tanner graphs for systematic raptor codes in order to increase the efficiency of soft decoding. A modified Tanner graph is drawn in terms of bit and check nodes for each component code, instead of encoding and information nodes, as in conventional Tanner graphs, for its component Luby transform codes. This modified Tanner graph enables the use of a more simplified soft iterative decoding algorithm and provides improved decoding performance compared with the conventional method. In addition, they propose an efficient joint iterative soft decoding method with a parallel process to speed up the iterative decoding. The simulation results in this study reveal that the modified Tanner graph works better than the conventional Tanner graph for joint iterative decoding, and that the proposed parallel decoding method can contribute to further enhance the performance as well as the decoding speed by reducing the average number of iterations. © 2015. The Institution of Engineering and Technology. Source


Zhang M.,Chonbuk National University | Kim S.,Chonbuk National University | Kim W.-Y.,Comesta Inc. | Cho Y.-H.,Comesta Inc.
2012 6th Advanced Satellite Multimedia Systems Conference, ASMS 2012 and 12th Signal Processing for Space Communications Workshop, SPSC 2012 | Year: 2012

This paper presents a new bit-interleaved higher-order APSK scheme for LDPC codes. Although the maximum decoding performance can be achieved using the maximum likelihood (ML) soft detection scheme, the complexity increases exponentially with the modulation orders. We approximate the ML soft detection scheme by applying the hard decision threshold (HDT) based method for a modified constellation of 32-APSK. In order to further improve the BER performance, we combined an efficient bit interleaving scheme, by considering that BER performance of each bit contained in a symbol is not uniform. Simulation results demonstrate that the proposed bit-interleaved scheme with very simple HDT based soft detection can achieve better performance compared to the ML detection of conventional scheme. © 2012 IEEE. Source

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