• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1433-1441
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• 2011

Design rules of optical transmission links with dispersion management (DM) and optical phase conjugation (OPC) for compensating optical signal distortion due to chromatic dispersion and self phase modulation (SPM) of single mode fiber (SMF) are investigated in this paper. Design rules consist of optimal net residual dispersion (NRD) and optimal range of launching power of wavelength division multiplexed (WDM) channels as a function of total transmission length and span length. In all considered total transmission length and span length, optimal NRD are obtained to +10 ps/nm and -10 ps/mn for transmission links, which is controlled by precompensation and postcompensation, respectively. It is confirmed that system performances are more improved and effective NRD for wide launching power have wider range as total transmission length and span length are more decreased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.226-233
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• 2009

A novel frequency offset estimation scheme using a periodogram is proposed for orthogonal frequency division multiplexing (OfDM) systems. A conventional scheme proposed by Ren has a problem that the fractional and residual frequency offset estimation steps do not compensate for the difference between the real frequency offset and estimated integer frequency offset in the noise channel. So, the frequency offset estimation performance of Ren's scheme is degraded. In this paper, a frequency offset estimation scheme is proposed, which has a larger estimation range than that of the factional and residual frequency offset estimation steps in Ren's scheme. The proposed scheme can compensate for the difference between the real frequency offset and estimated integer frequency offset, unlike Ren's scheme. From the simulation results, we can observe that the performance of the proposed scheme is better than that of Ren's scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.739-746
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• 2017

Orthogonal frequency division multiplexing(OFDM) systems have many advantages. However, OFDM systems are much affected by a nonlinear distortion because those systems have a high peak to average power ratio(PAPR) value. A selected mapping technology was suggested to reduce a PAPR value. The technology does not have data loss but receivers need side information to know modified phase sequence. Therefore, side information causes decreased a transmission efficiency. In this paper, we suggest a blind SLM receiver using a cross correlation technology. This receiver does not require side information. The proposed blind SLM receiver calculates sums of cross-correlation between transmitted pilot signals multiplied by each phase sequence and received pilot signals. So, this receiver detects side information which has a maximum sum cross-correlation value. We compared our proposed SLM receiver to a conventional blind SLM receiver through bit error rate(BER) and side information error rate(SIER) performances. Simulation results show that the proposed SLM receiver has improved BER and SIER performances than the conventional SLM receiver.

• Journal of the Korea Society of Computer and Information
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• v.25 no.5
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• pp.1-9
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• 2020

In this paper, we propose a model that performs more natural facial attribute editing by utilizing mask information in the hair and hat region. STGAN, one of state-of-the-art research of facial attribute editing, has shown results of naturally editing multiple facial attributes. However, editing hair-related attributes can produce unnatural results. The key idea of the proposed method is to additionally utilize information on the face regions that was lacking in the existing model. To do this, we apply three ideas. First, hair information is supplemented by adding hair ratio attributes through masks. Second, unnecessary changes in the image are suppressed by adding cycle consistency loss. Third, a hat segmentation network is added to prevent hat region distortion. Through qualitative evaluation, the effectiveness of the proposed method is evaluated and analyzed. The method proposed in the experimental results generated hair and face regions more naturally and successfully prevented the distortion of the hat region.

• Korean Journal of Optics and Photonics
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• v.27 no.4
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• pp.133-142
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• 2016

This paper presents the design and simulation of a three-dimensional pixel-by-pixel scanning light detection and ranging (LIDAR) system with a microelectromechanical system (MEMS) scanning mirror and direct sequence optical code division multiple access (DS-OCDMA) techniques. It measures a frame with $848{\times}480$ pixels at a refresh rate of 60 fps. The emitted laser pulse waves of each pixel are coded with DS-OCDMA techniques. The coded laser pulse waves include the pixel's position in the frame, and a checksum. The LIDAR emits the coded laser pulse waves periodically, without idle listening time to receive returning light at the receiver. The MEMS scanning mirror is used to deflect and steer the coded laser pulse waves to a specific target point. When all the pixels in a frame have been processed, the travel time is used by the pixel-by-pixel scanning LIDAR to generate point cloud data as the measured result.

• The Journal of the Korea Contents Association
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• v.15 no.2
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• pp.11-20
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• 2015

In this paper, we develop an intelligent mobile surveillance system based on binary CDMA for the unmanned automatic tracking and surveillance. That is, we implement a intelligent surveillance system using the binary CDMA wireless communication technology which is applied the merit of CDMA and TDMA on it complexly. This system is able to monitor the site of the accident on network in real time and process the various situations by implementing the security surveillance system. This system pursues an object by the 360-degree using camera, expands image using a PTZ(Pan/Tilt/Zoom) camera zooming function, identifies the mobile objects image within a screen and transfers the identified image to the remote site. Finally, we show the efficiency of the implemented system through the simulation of the controlled situations, such as tracking coverage on objects, object expansion, object detection number, monitoring the remote transferred image, number of frame per second by the image output signal etc..

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.5
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• pp.477-485
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• 2002

In this paper, we present an efficient hardware architecture for the H.263 video codec and its VLSI implementation. This architecture is based on the unified interface by which internal hardware engines and an internal RISC processor are connected one another. The unified interface enables the modular design of internal blocks, efficient hardware/software partitioning, and pipelined paralled operations. The developed VLSI supports the H.263 version 2 profile 3 @ level 10, and moreover, both the control protocol H.245 and the multiplexing protocol H.223. Therefore, it can be used for the complete ITU-T H.324 or 3GPP 3G 324M multimedia processor with the help of an external audio codec. Simultaneous encoding and decoding of QCIF format images at a rate greater than 15 frames per second is achieved at 40 MHz clock frequency.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.9
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• pp.9-17
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• 1999

In this paper, we present a mathematical modeling and perform a performance analysis of double-dwell serial search algorithm, which has a search window concept, for pilot channel in DS-CDMA(Direct Sequence Code Division Multiple Access). We derive a code detection function, a false alarm function, a code miss function, and a mean code acquisition time for the performance analysis. We calculate the mean code acquisition time of the mathematical model in IS-95 forward link and compare it with that of the conventional search methods. The performance of the code acquisition system is also evaluated to investigate the effect of dwell times and search window size. The JTC channel model, which is a PCS channel model in North America, is used for the analysis. The numerical result shows that the mean code acquisition time of the double-dwell serial search algorithm with a search window is reduced by about 17%~25% than those of the conventional ones.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.24-31
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• 2007

DVB-T (Digital Video Broadcasting-Terrestrial) is an important multimedia broadcasting technology capable of high data-rate transmission and adopted by Europe. OFDM (Orthogonal Frequency Division Multiplexing) is the backbone technique employed in DVB-T to support multimedia services that have various bandwidths. Unfortunately, an OFDM signal has a large PAPR (Peak-to-Average Power Ratio). In this paper, we investigate the performance of a simple PAPR reduction scheme for the DVB-T system, which requires no change of a receiver structure or no additional information transmission. The approach we employed is clipping in the time and frequency domains. The time-domain clipping is carried out with a predetermined clipping level while the frequency-domain clipping is done within EVM (Error Vector Magnitude). This approach is suboptimal with lower computational complexity compared to the optimal method. The simulation results demonstrate that the proposed one is getting more effective at lower modulation levels and with more allowed constellation error.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.29-34
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• 2007

This paper presents a novel photonic bandgap (PBG) structure for size reduction and linearity improvement in power amplifier. The proposed structure is a two-dimensional (2-D) periodic lattice patterned on a dielectric slab that does not require nonplanar fabrication process. Throughout the experi-mental results, this structure has more broad stopband and high suppression performance than conventional three cell PBG and distorted uniplanar compact-PBG (DUC-PBG). This new PBG structure can be applied with power amplifier for linearity improvement. The 3rd intermodulation distortion (IMD3) of the power amplifier using new PBG structure is -36.16 dBc for (code division multiple access) CDMA applications. Compared with power amplifier without the proposed PBG structure, improved IMD3 is -13.49 dBc.